


r-^^. 



-^j. 
^ 



<^^ *'^''\^ 











.-tOx. 










.■*•' »• 







« • o 







.<• 



HOx. 





« » • 






6°^ 










Showing Method of Determining Elastic Behavior of Concrete Bars, 6x6-Inches in Cross- 
Section. Specimen, with Electric Extensometer Attached, Mounted for Compression in 
the 150,000 Pound Emery Testing Machine of Columbia University. 



CEMENTS, 
MORTARS AND CONCRETES 



THEIR PHYSICAL PROPERTIES 



BY 

Myron S. Falk, Ph. D., 

M 
INSTRUCTOR IN CIVIL ENGINEERING IN COLUMBIA UNIVERSITY 

IN THE CITY OF NEW YORK. 



y 



NEW YORK 

M. C. C LARK 

1904 






f- '^SiaSKjUHrMOtai 



UBORW/ rtf Q0N6RE3S 
Tm Oooies Rtirm%ti 

OCT 3 1904 
Oooyrtftit Entry 

OLA^ a XXo. Na 

COPY B 

inimiiijii III I 




copyright, 1904, 
MYRON S. FALK. 



• • « 



INTRODUCTION. 



The purpose of this treatise has been to set forth as concisely 
as possible the physical properties of cement and cement mix- 
tures, with principal reference to those properties which concern 
the engineer. The results of investigations made upon these ma- 
terials have been examined with great care. Engineers desiring 
such data on cements, mortars and concretes, have hitherto been 
obliged to refer to numerous scattered articles and books. It 
has been the author's object to abstract, classify and summarize 
•all the reliable data extant, filling in certain gaps with data of his 
own. The following headings outline, for the greater part, the 
scope of the work: 

General Physical Properties : 

Changes in Volume When Setting. 

Coefficient of Expansion Due to Temperature Changes. 

The Action of Sea Water and Salt. 

Porosity and Impermeability. 

Effect of Freezing. 

Adhesion of Iron Rods to Cement Mixtures. 

Fatigue of Cement Mixtures. 

General Elastic Properties : 

Tensile and Compressive Properties. 
Coefficient of Elasticity . 
Elastic Limit. 
Ultimate Resistance. 

Flexural Properties. 

Coefficient of Elasticity . 
Modulus of Rupture. 

Shearing Resistance. 

The sources from which the experimental data have been ob- 
tained are furnished, in every instance, with those data; it is 



iv INTRODUCTION. 

therefore unnecessary to give separate credit to the various ex- 
perimenters at this point. It is proper to say, however, that use 
has been made only of those results which gave evidence of care- 
ful work, so that no conclusions might be invalidated by reason 
of the unreliability of the experiments. Free use has been made 
of the Annual Reports of the Watertown, Mass., Arsenal, of the 
Transactions of the American vSociety of Civil Engineers, and of 
the Proceedings of the Institution of Civil Engineers of Great 
Britain. The experiments, not previously published, made under 
the author's direction in the laboratories of Cokmibia University, 
have also been included. 

It is believed that the results obtained relating to the elastic 
properties of the material, such as the values of the coefficients 
of elasticity and the ultimate strengths, have been so analyzed 
that these values may be determined in advance, for any mix- 
ture, within small limits of error; but future experiments and 
future improvement in the manufacture of cement mixtures may 
cause considerable changes in these figures. 

In order that a cement's physical peculiarities may be more 
clearly comprehended, it has been thought advisable to consider 
as a preliminary some of the chemical characteristics of cements. 
In connection with the discussion of chemical compositions, the 
theories of the setting of cements have therefore been analyzed, 
and it has been possible to abstract, in an appendix, Mr. Clif- 
ford Richardson's theory as to the constitution of Portland 
cements. In addition, a chapter, together with an appendix, 
treating briefiy of the ordinary commercial tests has been in- 
cluded. M. S. F. 

August 22, 1904. 



CONTENTS. 



CHAPTER I. 
CHEMICAL PROPERTIES OF CEMENT. 

ABT. PAGE 

1. Theories of Setting ; I 

2. Chemical Analyses 3 

Portland Cements 3 

Natural Cements 6 

CHAPTER II. 
PHYSICAL TESTS OF CEMENT. 

3. Commercial Physical Tests 9 

4. Specific Gravity Tests 10 

5. Fineness Test II 

6. Test for Time of Setting 13 

Action of Plaster of Paris 14 

Temperature Affects Time of Setting 16 

Retarding the Set 17 

Temperature Changes During Setting 18 

7. Tests of Tensile Strength 19 

8. Ratio of Compressive and Tensile Strengths 26 

9. Variations in the Making of Tensile Tests 29 

10. Variations of Sands in Tensile Tests 30 

Effect of Clay in Sand ". 34 

1 1. Test of Constancy of Volume 39 

CHAPTER III. 
GENERAL PHYSICAL PROPERTIES. 

12. Variation in Volume of Cement Moriars in Air and Water 40 

13- The Coefficient of Expansion Due to Temperature Changes 43 

14. The Action of Sea Water on Cements 45 

Strength in Sea Water 47 

Gauging with Salt Water 50 

15. Porosity and Permeability 51 

Feref s Conclusions 52 

16. The Effect of Freezing on Cement Mixtures 55 

17. Adhesion of Iron in Concrete 61 

18. The Fatigue of Cement Mixtures 66 



vi CONTENTS, 

CHAPTER IV. 

ELASTIC PROPERTIES IN GENERAL. 

19. Treatment of Stress-Strain Curves 70 

CHAPTER V. 
TENSILE PROPERTIES. 

20. Coefficient of Elasticity and Ultimate Resistance 75 

Conclusions 97 

CHAPTER VI. 
COMPRESSIVE PROPERTIES. 

21. Coefficient of Elasticity and Ultimate Resistance 99 

22. Ultimate Compressive Resistance 121 

Setting Under Water 1 30 

IV et or Dry Concretes 130 

High Temperatures 132 

23. Conclusions 132 

CHAPTER VII. 

FLEXURAL PROPERTIES. 

24. The Theory of Flexure as Applied to Concrete 142 

25. Flexural Coefficient of Elasticity 144 

26. Modulus of Rupture in Bending 149 

27. Shearing Resistance and Conclusion 157 

APPENDIX I. 

Report on Uniform Tests of Cement by the Special Committee of the 

American Society of Civil Engineers 159 

Sampling, 159; Chemical Analysis, 159; Specific Gravity, 160; Fineness, 
161; Normal Consistency, 162; Time of Setting, 163; Standard Sand, 
164; Form of Briquette, 164; Moulds, 164; Mixing, 165; Moulding, 
165; Storage of the Test Pieces, 166; Tensile Strength, 166: Constancy 
of Volume, 167. 

APPENDIX II. 
Constitution of Cement 169 

Index 171 

Authors' Index 175 



CHAPTER I. 

CHEMICAL PROPERTIES OF CEMENT. 

Definition — Cement is a material which has the property of set- 
ting and hardening under water, and is composed principally of 
lime, silica and alumina. Two forms of cement are commonl}^ 
recognized, natural and Portland, and to these the following 
pages will be entirely restricted. The difference between these 
forms is principally one of manufacture; the basic principles in 
both varieties are the same. 

Article i. — Theories of Setting. 

The proper chemical constitution of cements involves the con- 
sideration of the theory of the setting and hardening of cements, 
the reasoning concerning which is, at the present time, not unani- 
mous. Chemists have not definitely determined the chemical 
changes that occur when water is added to dry cement; but the 
conclusions reached by Le Chatelier in 1887 ^^^ by the New- 
berrys in 1897 have been accorded more weight than those of 
others. 

Ze Chatelier' s Theory (Annales des Mines ^ iSSy, p. 34S)' 
Le Chatelier considers that when the raw materials of a cement 
have been burned two different sets of compounds possessing the 
property of setting and hardening upon the addition of water may 
be formed. 

In the first case he considers that the finished material contains 
lime (CaO) just sufficient in amount to combine with the silica 
(SiOg) and alumina (AlaO^J to form tricalcic silicate (3CaO.Si02) 
and tricalcic aluminate (3CaO.Al203). These compounds, upon 
hydration, set and harden. He finds it unnecessary to provide lime 
to react on the sesquioxide of iron which may be present in the 



2 CHEMICAL PROPEFTIES OF CEMENT, [Ch. L 

mixture, since the calcic ferrites that might form fall to powder 
upon the addition of water. Magnesia (MgO) and lime he con- 
siders as possessing equivalent properties, and, therefore, inter- 
changeable. In this case, then, no multiple silicates of alumina 
and lime are formed; and in order that the finished cement may 
have no free lime existing in it, Le Chatelier states that the pro- 
portion of lime and magnesia to silica and alumina should be 
subject to the following conditions: 

CaO-^Mg O ^ 

The objection to the presence of free lime or magnesia is due to 
the fact that they blow or expand in volume when acted upon by 
water; disintegration of the cement follows and it becomes unfit 
for use. 

For the second condition Le Chatelier believes that only tri- 
calcic aluminate and a silico-aluminate of lime, represented by 
2Si02-Al203.3CaO, are formed, and that the FcgOg acts similarly 
to AI2O3 in the case of multiple silicates and need not be sepa- 
rated from it. 

For this case Le Chatelier states the condition of the propor- 
tions of the constituent's as follows: 

CaO-\-MgO ^ 

StO-Al,0,-Fe,0,=' ^ 

The Newberrys' Theory (J. Soc. Chem. Ind,, i8gy, p. 88g). 

The conclusions reached by Spencer B. and W. B. Newberry 
are quite different; it is their belief that the compounds that 
harden, upon hydration, are tricalcic silicate and dicalcic alumi- 
nate, and not tricalcic aluminate. 

Tricalcium silicate requires 2.8 parts of weight of lime to I part 
of silica, and dicalcic aluminate requires i.i parts of lime to i of 
alumina. The Newberry formula for a theoretically perfect ce- 
ment is therefore: 

2,8 Silica-\-i.i Alumina 

Lime 

In this equation the materials represent percentages of weight 
in the cement. 



Ait. 2.] CHEMICAL ANALYSES. 3 

The Newberrys also conclude that FcgOg acts similarly to 
AI2O3, but should not be allowed in excess of 5 per cent. In 
this they differ from Le Chatelier. Again, Le Chatelier's for- 
mula places magnesia and lime of equivalent value in a cement; 
the Newberrys, on the contrary, consider magnesia inactive, and 
to perform no useful function. 

One general opinion concerning the magnesian compounds in 
cement is that they cause the first or preliminary setting of the 
cement, but that they expand and crack after aging. In all cases 
the calcic compounds are considered to be the ones which harden 
with age, and they are the compounds which cause ultimate 
strength. On account of this possibility of blowing, it is there- 
fore the common practice at present to limit the presence of mag- 
nesia to 5 per cent. Cements containing up to this limit have not 
been shown to be inferior. 

Another theory as to the first or quick setting properties of 
cement attributes these properties to the presence of calcium- 
aluminate, and the final or ultimate strength to the calcium- 
silicate only. It is difficult to reconcile these conflicting opinions. 

Other chemical elements which appear in a cement are be- 
lieved to be of no practical importance, and none other will be 
considered, except plaster of Paris or sulphate of lime, CaSO^, 
which is added in percentage never exceeding 2 per cent., for the 
purpose of causing a slower setting of the cement. This is a 
common practice, and its effect on the strength of the cement will 
be considered later. 



Art. 2. — Chemical Analyses. 

It will be interesting to examine the different chemical com- 
positions of cement as they have been recorded by different 
analysts. It will be found that the variations of the different 
constituents, on the whole, are very slight. 

Portland Cements — Table I. exhibits the values of analyses as 
taken from the report of the Watertown Arsenal "Test of Metals, 
etc.," for 1901. 



CHEMICAL PROPERTIES OF CEMENT, 



[Ch. I. 



TABLE I.— PORTLAND CEMENTS. 



Brand 



Alpha 

Atlas 

Lehigh 

Star (with plaster) 
Star (without " ) 

Storm King 

Whitehall 

Alsen 

Dyckerhoff 

Josson 



Average 



Location of Works 



Easton, Pa . . . . . 
Northampton, Pa 
West Coplay, Pa 
Siegfried, Pa- . . . 



Akron, N. Y... 
Cementon, Pa 
Germany 



Belgium. 



Si02 



20.60 
18.32 
23.84 
22.00 
22.45 
22.94 
20.30 
20.42 
20.04 
22.92 



Oi 



Fe2 0t 



2.91 
3.36 
L30 
2.50 
2.53 
2.90 
2.95 
2.10 

3.95 
2.46 



21.38 I 2.70 



AlsO; 



CaO 



IL20|59. 

11.22 60. 
8.I26I, 
9.00 59. 
9.27 60, 
6.30'43. 

10.87162, 

11.00 57, 
7.48 63, 
7.9863, 



MgO 



3.25 
3.78 
2.48 
3.50 
3.59 

*20.72 
2.51 
2.53 
1.23 

Trace 



9.23 60.76 2.54 1. 61 1. 64 



32 



C/3H 



SOs 



ea.- 

UQ 



CO2 



1.34 
1.92 
1.08 
0.75 
1. 00 
1.00 
0.12 
4.19 
62j3.00 
28 1.97 



*Not included in average. 



TABLE IL— PORTLAND CEMENTS. 



Brand 



Alpha 

Atlas 

Giant 

Saylors. . . . 
Vulcanite . . 
Empire. . . . 

Jordan 

Diamond.. . 
Sandusky. . 
Bronson . . . 
Whitecliffs. 



Average , 



Location of Works 



Jordan, N. Y.. 
Coplay, Pa. . . . 
Vulcanite, N. J. 
Warner, N.Y.. . 



Middlebranch, Ohio 



Bronson, Mich 
Whitecliff, Ark 



SiOo 


AI2O3 


FesOs 


CaO 


MgO 


22.62 


8.76 


2.66 


61.46 


2.92 


21.96 


8.29 


2.67 


60.66 


3.43 


19,92 


9.83 


2.63 


60.32 


3.12 


22.68 


6.71 


2.35 


62.3 


3.14 


21.08 


7.86 


2.48 


63.68 


2.62 


22.04 


6.45 


3.41 


60.92 


3.53 


2L86 


7.17 


3.73 


6LI4 


2.34 


2L8 


7.95 


4.95 


6L9 


1.64 


23.08 


6.16 


2.9 


62.38 


1. 21 


20.95 


9.74 


3.12 


63.17 


.75 


22.93 
21.90 


^10.33-^ 


64.67 


.94 


7.89 


3.09 


62.04 


2.33 



SOa 



1.53 
1.43 
1. 13 
1.88 
1.25 
2.73 
1.94 

.79 
1.66 

.86 
L05 

1.49 



TABLE in. —EUROPEAN PORTLAND CEMENTS. 



Brand 



White label, Alsen 

Dyckerhoff 

Germania 

Hcmmoor 

Lagerdorfer , 

Brook, Shoobridge & Co 

Francis 

Condor 

Candlot, French 

Boulogne, French 



Average . 



SiOa AI2O3 Fe203 CaO 



20.48 

20.64 

22.08 

21.14 

23.55 

22.2 

22.18 

23.87 

22.3 

22.3 

22.07 



7.28 

7.15 

6.84 

5.95 

7.47 

7.35 

8.48 

6.91 

8.5 

7. 

7.29 



3.88 

3.69 

3.36 

4.01 

2.4 

4.77 

5. 08 

2.27 

3.1 

2.5 

3.51 



64.3 

63.06 

63.72 

63.24 

61.99 

61. 46 

61.44 

64.49 

62.8 

64.62 

63.12 



MgO 



L76 
2.33 
1.32 
1.44 
1.42 
1.35 
1.34 
1.04 
.45 
LO4 

1.35 



SO3 



2.46 
1.39 
L82 
1.47 
L07 
1.87 
1.56 

.88 

.7 

.75 

1.40 



Art. 2.] 



CHEMICAL ANALYSES. 



Table II. shows similar quantities obtained from analyses of 
American cements, compiled by Ries & Eckels, in "Lime and 
Cement Industries of New York," 1901, page 705. 

Table III. is taken from the same book and exhibits the com- 
position of sorae European Portland cements. 







TABLE 


IV. 






CaO 


Si02 


AI2O3 


FeoQs 


MgO 


SO3 


60.94 


23.23 


7.75 


3.04 


2.14 


1.56 



Table IV. shows the average results of chemical analyses made 
on thirty-eight samples of cement used in submarine work on the 
Charlestown bridge, Boston, by the Boston Transit Commission, 
as published in their report for 1900. 

Finally, owing to the interest which has been aroused by the 
novel conditions of manufacture, Table V., containing an analysis 
of the Edison Portland Cement Company's cement, is given. 
The analysis is taken from a reported test by Lathbury & Spack- 
man, Incorp., of Philadelphia, and was published in the "Engi- 
neering Record" December 26, 1903. 







TABLE V. 






CaO 


SiOo 


AI2O3 


FeoOs 


MgO 


62.71 


20.14 


7.51 


3.33 


2.34 



These tables show very uniform results; in general, the per- 
centages of the constituents are as follows : 



CaO 

MgO 

SiO^ 

Al,03 

Fe203 



averages 62% 

" 2% 

" 22% 

" 8% 

'' 3% 



Inserting these values in the Newberry formula, the result ob- 
tained is 



CHEMICAL PROPERTIES OF CEMENT. 
2.8X22+1. iX8 



[Ch. I. 



62 



= 1.14, 



or an error of 14 per cent, as compared with a theoretically per- 
fect cement. 

By substitution the first of Le Chatelier's formulas reduces to 

62+2 



and the second to 



22+8' 
62+2 



:2.I3; 



22—8—3 



^5.82 



These values are respectively smaller and greater than 3, as 
they should be; but they give no indication of the standard of ex- 
cellence obtained. 

Natural Cements — The following tables show the average an- 
alyses of both European and American natural cements : 

Table VI. is taken from the Watertown Arsenal report on 
"Test of Metals" for 1901; Table VII. from U. Cummings's 



TABLE VI.— NATURAL CEMENTS. 



Brand 



Akron Star 

Austin 

Bonneville Improved. 

Hoffman* 

Mankato 

Newark & Rosendale. 

Norton 

Obelisk 

Potomac 



Location of Works 



Akron, N.Y 

Mankato, Minn. 
Siegfried, Pa. . . . 
Rosendale, N. Y. 
Mankato, Minn. 
Whiteport, N.Y.. 
Binnewater, N.Y. 
Akron, N. Y 



Average. 



SiOa 



20.40 
19.02 
30.40 
25.00 
27.70 
28.71 
26.66 
23.70 
32.00 



Fe2 0j 



2.56 
1.24 
2.60 
2.27 
1.86 
3.60 
3.02 
3.30 
2.70 



AI2O3 



6.22 

8.96 

10.36 

8.93 

7.06 

5.88 

11.48 

16.70 

8.79 



CaO 



40.64 
41.18 
52.12 
39.30 
37.00 
27.00 
38.33 
37.00 
33.89 



25.95 2.57 9.37 38.49 19.02 1.55 2.54 



MgO 



25.8O 
26.58 
0.21 
16.18 
22.63 
30.00 
I6.4I 
15.30 
18.10 



SO3 CO2 



2.91 
1.27 
1.24 
1.40 
1.23 
1.30 

1.35 
L98 
1. 31 



1.47 
1.75 
3.07 
2.66 
2.46 
3.52 
2.75 
2.00 
3.20 



^Contains 4.26 per cent, of Oxides of Sodium and Potassium. 

"American Cements," and Table VIII. from analyses, reported 
by D. J. Whittemore, in the Transactions of the American Society 
of Civil Engineers, 1880. 

The American natural cements of Table VII. cover a wi4e 
range of territory. 



Art. 2.] 



CHEMICAL ANALYSES. 



TABLE VII.— NATURAL CEMENTS.* 



Brand and Location of Works. 



Buffalo Hydraulic Cement ; Buffalo, N. Y 

Utica, III 

Milwaukee, Wis 

Fernleaf Brand; Louisville, Ky 

Hulme; Louisville, Ky 

N. L. & C. Co.; Rosendale, N. Y 

Rocklock; Rosendafe, N. Y 

N. Y. & R.; Rosendale, N. Y 

Hoffman; Rosendale, N. Y 

Norton High Falls; Rosendale, N. Y 

Cumberland, Md 

Napanee, Ont 

Newman; Akron, N. Y 

Cummings; Akron, N. Y 

South Riverside, Cal 

Brockett; Ft. Scott Hydraulic, Kansas City, Mo. • • • 

Utica Brand; Utica, 111 

Shepherdstown, W. Va . 

Howard Hyd. Cem.; Cement, Ga 

Hydraulic Cem. Rock; Platte River, Neb.. 

Mankato, Minn 

St. Louis Hydraulic Cement, near E. Carondelet, 111. 

Barnesville, Ohio 

Warnock, Ohio 

Austin, Minn 

Round Top Cement; Hancock, Md 

Balcony Falls, Va 



SiOo 



24.3 

34.66 

23.16 

26.4 

25.28 

30.5 

29.98 

30.84 

27.3 

27.98 

28.38 

19.9 

22.62 

26.69 

24.34 

23.32 

27.6 

33.42 

22.58 

22.44 

28.43 

22.21 



AloOj 



2.61 

5.1 
33 
28 
85 
84 
88 
75 
14 
28 



n.7I 
5.92 
7.44 
7.21 
8.56 
6.99 

10.6 

10.04 
7.23 
6.7 
6.71 

16.48 



32.06i2I.27 
28.45! 2.24 
I8.59i 9.14 
28.02! 10.2 
25.15i 8. 



FeoO; 



6.2 

I. 

1. 71 

L 

1.43 

2.42 

2.5 

2. 1 1 

1.8 

L7 

2.29 

1. 14 

1.4 

1.3 

2.08 

5.97 

.8 
6. 

3.35 
2. 

1.94 
1.67 
2. 1 1 
2. 
L 

8.8 
3.28 



CaO 



39.45 

30.24 

36.08 

45.22 

44.65 

34.38 

33.23 

34.49 

35.98 

37.59 

43.97 

46.75 

40.68 

43.12 

61.62 

53.96 

33.04 

32.79 

48.18 

32.73 

36.31 

39.64 

35.56 

56. 

40.7 

44.48 

49.53 



MgO 



6.16 
18. 
20.38 

9. 

9.5 
18. 
17.8 
17.77 
18. 
15. 

2.21 
16. 
22. 
19.55 
.4 

7.76 

7.26 

9.59 
15. 

.67 
23.89 
17.5 

7. 
10. 
27. 

L 
13.78 



Average. 



26.40 8.17 2.55 41.12 12.97 



*From "American Cements," by U. Cummings 



TABLE VIIL— NATURAL CEMENTS. 



Cement No. 


CaO 


MgO 


SiOs 


AI0O3 


FeaOs 


I 


45.17 
36.32 
33.97 
40.75 


16.52 
14.47 
15.21 
25.25 


23.40 
24.50 
28.04 
22.22 


8.07 
14.32 
12.82 

8.68 


2.45 


2 


2.93 


3 


4.60 


4 


LI8 






Average. . 


39.05 


15.36 


24.54 


10.97 


2.79 



The results show that 



CaO averages 40 % 

MgO " 15 % 

SiO^ " 26 % 

AI2O3 " 81% 

Fe,03 " 24% 



8 CHEMICAL PROPERTIES OF CEMENT, [Ch. I. 

It will be seen that the greatest difference between the natural 
and Portland cement is in the varying proportions of the lime 
and magnesia contents; the other constituents remain about the 
same. Using the average figures of the natural cements given 
on the preceding page, the Newberry formula becomes 

2.8X26+1. 1X8A 

— - — — ^^-^=2.05 ; 

40 

the first of Le Chatelier's formulas becomes 

40+15. 



and the second, 



26+8 J 
40+15 



1.6 



26—84—2 



^=Z'^7 



None of these formulas furnishes results comparable with theo- 
retic requirements, in the case of the Newberry formula pro1)ably 
on account of the neglect of the magnesia. 

As a conclusion it is evident that a chemical analysis may give 
no final indication of the quality of the cement. Adulteration of 
the cement with inert material, such as slag, may be discovered. 
Certain materials, such as magnesia or plaster of Paris, may be 
found present in too large quantities; but it seems evident that a 
poor cement may be due more to imperfect manufacture than to 
the use of improper constituents. 



CHAPTER IL 

PHYSICAL TESTS OF CEMENTS. 

The mechanical operations attending the manufacture of ce- 
ment, such as the mixing, burning and grinding of the raw ma- 
terials, bear intimate relation to the final physical properties of 
the cement, and should be analyzed just as closely as the chemical 
compositions; but in this treatise it is out of place to discuss 
manufacturing operations. The manufacture of a cement is 
therefore to be assumed correct if a sample of it passes those 
physical tests which are made for the purpose of determining its 
acceptance or rejectance for use. These tests are of such a char- 
acter that the results of all experimenters are comparable; but it 
is not necessary, although it is desirable, that these tests should 
furnish values of the strength of the material, values which might 
be used in designing engineering work. 

Art. 3. — Commercial Physical Tests. 

The physical tests require but brief explanation, and only those 
tests which are practiced in the United States need consideration. 
They are five in number: 

1. Specific gravity, 

2. Fineness, 

3. The time of setting, 

4. The tensile strength, and 

5. The constancy of volume. 

They are fully explained in the reports presented on January 
21, 1903, and on January 20, 1904, to the American Society of 
Civil Engineers by its Committee on ''Uniform Tests of Ce- 
ments." A copy of these reports is given in the appendix. 

Experience has shown that good cements furnish certain re- 



10 PHYSICAL TESTS OF CEMENTS. [Ch. II. 

suits in these standard tests, and it is to be expected that, if new 
cements fulfill the same conditions, their behavior in construction 
work will be the same. 

Art. 4. — Specific Gravity Tests. 

As stated in the first of the two reports mentioned above, the 
specific gravity of a cement is lowered by underburning, adul- 
teration and hydration; but the adulteration must be in consider- 
able quantity to afifect the result appreciably. When properly 
made, this test affords a quick check for underburning or adul- 
teration. 

Table I. exhibits the values of the specific gravity of repre- 
sentative Portland and natural cements, and is taken from the 
Watertown Arsenal Report on ''Tests of Metals" for 1901. The 
determinations were made with a Schumann volumeter, benzine 
being the liquid employed. 

Brand TABLE I. g^^^^i^V' 

Alpha Portland Cement 3- H 

Atlas Portland 3-09 

Storm King Portland 3-07 

Whitehall Portland (14 days after grinding) 3.13 

Alsen Portland 3-08 

Dyckerhoff Portland 3- 1 1 

Josson Portland 3.04 

Bonneville Improved Natural Cement 2.85 

Hoffman Natural 3.06 

Norton Natural 3-03 

Austin Natural 3-15 

Mankato Natural 2.93 

Newark & Rosendale Natural (I2 days after grinding) . . 3.06 

Obelisk Natural 3. 12 

Potomac Natural 2.94 

It will be seen that Portland cements give uniform results, the 
average of seven cements being 3.09. 

The specific gravity of the above cements after they had set 
was obtained in various ways. 

Table II. shows the specific gravity of the reground material 
after the cement had set for a period of three days. Different 



Art. 4.] 



SPECIFIC GRAVITY TESTS. 



11 



percentages of water were used, as indicated. It will be seen 

that in general the larger amount of water reduces the specific 

gravity. 

TABLE II. 



Brand 


Specific Gravity. — Material mixed with percentages of 
water of 




5% 


10% 


15% 


20% 


30% 


40% 








2.69 
2.82 
2.73 
2.77 




2.59 
2.73 




Lyckerhoff Portland. 

Bonneville Improved Nat'l 
Mankato Natural 


2.94 
2.69 
2.83 


2.88 
2.73 
2.80 




2.75 
2.77 


2.77 

2.67 







The specific gravity of the hydrated material in a cake of 
cement was also determined, as shown in Table IIL The ma- 
terial was weighed both in air and in water by means of a chemi- 
cal balance, account being taken of the water absorbed when the 
cement was immersed, thus making the necessary correction for 
voids. The cakes of material in this case were halves of tensile 
briquettes, but the report does not give the age of the briquettes ; 
there seems to be no difference in the values of those briquettes 
which set in air or in water. 

TABLE III. 



Brand 



Specific Gravity of Briquettes Which 
Set In 



Water 




Alpha Portland 

Dyckcrhoff Portland 

Bonneville Improved Natural 

Hoffman Natural 

Mankato Natural 

Atlas Portland (Material from 1 2 inch Cubes) 



2.29 
2.07 
1.66 
L77 
L66 
L92 to 2.17 



It will be seen that the specific gravity of the cement after set- 
ting is considerably less than the cement before the addition of 
water. 

Article 5 — Fineness Test. 

The fineness of a cement indicates to a great degree the pro- 
portion of inert material in it. Until lately it has been thought 
sufficient to measure the fineness of a cement with a No. 100 
sieve, but it is now becoming the practice to use a No. 200 sieve. 



12 



PHYSICAL TESTS OF CEMENTS, 



[Ch. II. 



As recommended by the American Society of Civil Engineers, 
these sieves should be made of woven cloth of brass wire which 
has the following diameters : 

No. 100 0.0045 inches 

No. 200 0.0024 inches 

The mesh should be regular in spacing and be within the follow- 
ing limits : 

No. 100 96 to 100 meshes to the linear inch 

No. 200 188 to 200 meshes to the linear inch 



The sifting is continued upon a sample until not more than 
one-tenth of i per cent, passes through after one minute of con- 
tinuous sifting. The percentage sifting through is found by 
weighing the residue and subtracting from the original quantity. 

There is naturally a commercial limit to the fineness of grind- 
ing of a cement; the following tables show characteristic results 
obtained from various well known brands of Portland and natural 
cements. 

Table I. is taken from the Report of the Watertown Arsenal 
''Test of Metals," etc., 1901 ; chemical analyses made on the dif- 
ferent sized particles of these brands show substantially the same 
composition which was found in the material taken from the 
barrels. 

TABLE I. 





Size of Grain 


Brand of Cement 


Greater Than 
.0058 Inch 


.0050 


.0034 


.0027 


Smaller Than 
.0027 




Corresponding to Sieve Having Meshes — 




98 X 100 


112x118 


155x170 


188x198 




Atlas Portland 

Star Portland 


II. 2 
12.9 
19.3 
14. 1 
33.6 
12.5 


3.8 
4.7 

1.9 


9.1 

10.4 

7.9 

6.4 


6.6 
II. 4 

8.2 
12.5 
23.8 
17.5 


69.3 
60.6 


Alsen Portland 

Hoffman Natural 

Mankato Natural 

Norton Natural 


58.9 
65.1 
42.6 
70.0 









Table II. is taken from Vol. VI. of ''Mineral Industry," and 
covers Portland cements only. 



Art. 5.] 



FINENESS TEST. 



13 



TABLE II. 



Brand. 



Say lor' s 

Giant 

Atlas 

Alpha 

Vulcanite 

Sandusky 

Brooks, Shoobridge & Co. 

Alsen 

Aalborg 

Condor 



Percentage Passing Sieve — 



No. 50 



100 

99 

99. 

99. 

99. 

99. 

98.8 

99.7 
100 

99.6 



No. 100 



96.4 
94.9 
92.7 
94.8 
95.3 
92.8 
88.3 
92.4 
99.6 
88.5 



No. 200 



68.4 
72.0 



As a matter of present day interest, the following test of the 
Edison Portland Cement Company's cement, from the same re- 
port previously mentioned, may be noted : 

Passed No. 100 sieve 99.8% 

Passed No. 200 sieve 91.6% 

Although two cements may furnish the same degree of fine- 
ness as to a No. lOO sieve, finer sieves may show different results. 
German experimenters have therefore employed the velocities 
and carrying capacities of liquids as a measure of fineness, but 
such refinement in testing is unnecessary. The No. 200 sieve 
furnishes a sufficient test. 

The tests which have been made upon cements to prove the 
superiority of fine grinding are not of great importance, and even 
in some cases show contradictory results. These are, however, 
easily explained. Neat unsifted cement, for instance, may show 
greater strength than the finely sifted, because the grains in the 
mixture may be better balanced, or because the coarser material, 
which is the harder burned, and usually the better, has been ex- 
cluded from the sifted. In the case of mortars the proportions 
and balancing of the sand greatly outweigh any results that may 
be obtained due tO' the sifting of the cement itself. The reader is, 
however, referred to experiments by Grant, Vol. XXL, Proc. 
Inst. Civ. Eng., and to Clarke, Trans. Am. Soc. C. E., Vol. XIV. 

Art. 6. — Test for Time of Setting. 

Two periods are noted in determining the time of setting of a 
cement: the initial setting, when the material first begins to set. 



14 



PHYSICAL TESTS OF CEMENTS. 



[Ch. II. 



and the final setting, when the material has acquired a certain 
degree of hardness. The former period determines the begin- 
ning of the process of crystallization, and is important to deter- 
mine, as a disturbance of the cement after the time of this initial 
setting produces loss of strength; but the time of setting never 
furnishes a gauge as to the ultimate strength of a cement. 

It is unnecessary to describe the apparatus used in this test; 
the report of the Committee of the American Society of Civil 
Engineers records in detail the methods of operation. 

Table L, taken from the Watertown Arsenal Report, 1901, 
shows some characteristic results of the time of setting of some 
standard American cements, when gauged with different per- 
centages of water ; the tests were made according to both Ameri- 
can and German standards. The dififerences for the varying per- 
centages of water are quite marked, the time of set increasing 
with the amount of water. There is also considerable difference 
in the results of the two methods of test. In general, it may be 
said that natural cements set faster than Portland. 



TABLE I. 



Brand 


Water 


Gillmore's Method 


German Method 


Per Cent. 


Initial Set 


Final Set 


Initial Set 


Final Set 


Alpha (Portland) \ 


20 
25 
30 
20 
25 
30 
30 
35 
40 
35 
40 
45 


H. M. 

2 20 

3 20 
5 40 

4 05 

5 10 
7 00 
2 15 

2 55 

3 43 

37 

47 

1 08 


H. M. 
5 00 
7 30 


H. M. 

35 
2 50 

4 40 

2 45 

3 35 

5 30 

1 25 

2 20 
2 48 

32 
40 

48 


H. M. 
4 25 
6 35 
8 40 

6 10 

7 05 


Atlas (Portland) < 

I 


7 10 

8 05 


Hoffman (Natural) \ 


3 25 
5 40 


2 55 
4 10 


Newark and Roscndalc j 
(Natural) 1 


I 17 

3 44 

4 18 


1 07 

2 19 

3 33 



Action of Plaster of Paris — The time of setting of a cement 
may be delayed by the addition of a small percentage of plaster 
of Paris. The action in that case is merely mechanical. The 
plaster of Paris dissolves m the water and forms a protecting 
covering about the cement particles ; at the same time it hardens 



Art. 6,] 



TEST FOR TIME OF SETTING, 



15 



and prevents action of the water on the cement. In small per- 
centages, plaster of Paris is found to increase the strength of ce- 
ments, but in large quantities expansion or blowing of the cement 
is likely to occur. The action in that case is similar to that of 
sea-water on cement. 

E. S. Wheeler, on page 2938 of the Report of the Chief of 
Engineers, U. S. Army, for 1895, records numerous tests show- 
ing the effect of plaster of Paris on the time of setting. An ad- 
dition up to 2 per cent, increases both the periods of initial and 
final set, but an addition of more than 2 and up to 10 per cent, 
decreases this period. It is not necessary to give the detailed 
figures of these experiments. 

Table II. is taken from the Report of the Chief of Engineers, 
U. S. Army, for 1896, p. 2832, and shows the varying values of 

TABLE II. 
Tensile Strength of Portland Cement witk Varying Percentages of 
Plaster of Paris, The sand is natural Point aux Pins, Each 
result is an ave^-age of five specimens. 



Plaster of Paris to Total Cement 



per cent 

1 per cent 

2 per cent 

3 per cent 
6 per cent 

per cent 

1 per cent 

2 per cent 

3 per cent 
6 per cent 



Ratio of Cement 
to Sand 



Strength in Lbs. Per Sq. Inch at Age of— 



7 Days 



487 
626 
600 

380 
323 
388 
360 
289 
192 



6 Months 



743 
746 




754 




742 





660 




492 


487 


530 


515 


547 


610 


607 


588 


663 


647 



1 Year 



the tensile strength of a Portland cement with the addition of 
various percentages of plaster of Paris. It will be seen in gen- 
eral that an addition of plaster of Paris up to 2 per cent, has no 
weakening effect. This is shown both for neat cement and for a 
cement mortar of i part of cement to 2 of sand. Again, it will 
be seen that the mortar in which the cement contained a large 
amount of plaster of Paris attained considerable strength at the 
age of one year. The report noted records tests on three brands 
of Portland cements and on some natural cements; the results 



16 



PHYSICAL TESTS OF CEMENTS. 



[Ch. II. 



are similar to those in the table; but many of the natural cements 
checked and disintegrated before the time of testing. The effect 
of the addition is seen to give very variable results, but a safe 
limit is 2 per cent. 

The time of setting of a cement depends also on its chemical 
composition and on the character of its burning. In general, a 
lightly burned cement sets quicker, as does also a freshly burned 
cement; but there are frequent exceptions. The quantity of 
water used in gauging the cement, the temperature of the water 
and the temperature of the air all afifect the time of setting. A 
rise of temperature follows the setting of all cements, and this 
rise increases very rapidly for fast setting cements. The time of 
setting is also affected by the volume of cement mixed. 



TABLE HI. 



Compressive Strength in 
Pounds per Square Inch 
when regauged after an 
interval of — 








Brand 








c 
jt 

u 
as O 
.no, 
a 

< 


Dyckerhoff 
Portland 


•V 

c 
o 

w5 


Storm King 
Portland 


c 
.2 

<n 

o 


Austin 

Natural 


c 
o 
CQ 


"3 
2^ 


Hours After First Mixing 


1 




I 


7279 


3549 
3667 
3412 


3489 


1792 
1599 


3328 


719 
724 


895 


713 


2 


6169 


3737 


3498 


387 


443 


3 

4 


7146 
6774 
6539 


3402 
2686 
2439 
2312 
1893 
1745 
1758 
1666 
1690 


3753 
3903 
3889 


1495 
II5I 


3827 
3696 


340 
276 


388 
*425 


340 


6 


424 


a 


378 


Tft 










12 














^A 










16 














TA 
















Oft 































*After seven hours. 

Temperature Affects Setting — Gen. Gillmore, in his Treatise on 
Limes, Mortars and Cements, page 83, shows some interesting 
results as to the variations in time of setting due to changes of 
temperature of water used in mixing. * It is unnecessary to re- 
produce here his results, but he shows that invariably high tem- 
peratures increase the rapidity of setting. There may be marked 
differences in the variations for different cements, but the state- 



Art. 6.] 



TEST FOR TIME OF SETTING. 



17 



ment is true of all. Exactly similar results are recorded by E. 
S. Wheeler in the Report of the Chief of Engineers, U. S. Army, 
1895, page 2936. 

Retarding the Set — If agitated sufficiently, it is possible to pre- 
vent a cement from setting at all; if disturbed after the final set- 
ting has commenced, its strength is greatly decreased, and since 
natural cements, as a class, reach their final set in periods of time 
considerably less than Portland cements, it may be expected that 
the effect of regauging the natural cements is of greater conse- 
quence. This is clearly shown by Table III., which is taken 

TABLE IV. 



Ult. Compressive Strength 
in Pounds per Square Inch 
after elapse of X hours be- 
tween initial mixing and 
placing of material in 
moulds 



Hours 



I 

2 

4 

6 

8 

10 

12 

14 

16 

20 



Brand of 
Cement 


u 

CO 

"r-s 


u 
« 

•OJ5 

so- 




2^ 
w5 


5467 


2414 


4665 


2594 


6421 


256I 


5470 


2167 


2718 


2282 


2662 


2021 


2387 


1842 


2160 


I54I 


2214 


1242 


2154 


1426 


I9OI 


1499 



Ult. Compressive Strength 
in Pounds per Square Inch 
after elapse of X hours be- 
tween initial mixing and 
placing of material in 
moulds 



Hours 

24 

30 

36 

42 

50 

60 

70 

80 

90 

100 



Brand of 
Cement 



no, 

03 



1669 

1442 

1279 

II32 

1 168 

1 150 

1001 

763 

723 

681 



flu-S 



1462 

I2I6 

IIOI 

1143 

1069 

IIIO 

849 

834 

782 

737 



from the Watertown Arsenal Report for 1901, and exhibits the 
results obtained in retarding the setting of cements which, after 
having been mixed with water, were left undisturbed until each 
of the periods shown, when a sample from the main batch was 
extracted. 

The majority of these specimens were 6 inch cubes, although 
some were smaller sized cubes. Many of the results obtained 
were averages of two or more samples, and the average age of 
the specimens was about thirty days. In this set of experiments 
the main batch of the cement was left undisturbed until the sam- 



18 



PHYSICAL TESTS OF CEMENTS, 



[Ch. II. 



pies were extracted, when the entire mass was again gauged with 
water; the sample was then tamped into a mould and allowed to 
set without further interference. 

Table IV. shows the compressive strengths attained when the 
main batch of the cement was not left undisturbed after the initial 
mixing, but kept in a continual state of agitation in the mixing 
bed. In this test the two kinds of cement used were both Star 
Portland, but one contained plaster of Paris, as a restrainer to 
control the time of setting, while the other contained no plaster. 
The effect of the restrainer is clearly shown. 





TABLE V. 








Brand of Cement 


Percentage of 
Water 


Maximum 

Temperature 

in Degrees 

Centigrade 


Ultimate 

Compressive 

Resistance 

in Pounds 

per Sq. Incii 


Age 

in 

Days 


Weiglit 

per 
Cu. Ft. 
in Lbs. 


Alpha Portland 

Star Portland 


26.2 
26.5 
27.0 
25.2 
25.0 
29.7 
22.7 
37.6 
35.0 
36.5 
40.0 
44.6 
41.8 


95. 
76. 
42.5 
103.5 
63. 
51. 
81. 5 
39.5 
37.5 
34.0 
35.0 
40.0 
39.0 


5706* 

1547 

4872 

840 
349 


9 

13 
9 

13 

8 


133.4 


Storm King Portland. . 
Whitehall Portland.... 
Dyckcrhoff Portland.. 

Josson Portland 

Atlas Portland 

Bonneville Natural. • . • 

Obelisk Natural 

Hoffman Natural 

Austin Natural 

Mankato Natural 

Norton Natural 


130.9 

137.5 

1 16.7 
II5.I 



*Not ruptured. 

Temperature Changes During Setting — Table V. shows the 
temperatures acquired by cements during setting; these values 
have been abstracted from the Watertown Arsenal Report for 
1901. Experiments were made on 12-inch cubes, the upper sur- 
face being exposed to the air. The thermometer bulbs reached 
to the centre of the cubes. It is interesting to note that the 
highest temperatures were reached by Portland cements as a 
class, in some cases exceeding the boiling point of water. A 
number of hours elapsed before the maximum temperature was 
obtained, generally six to twelve hours for a neat Portland ce- 
ment, while a 1:1 mortar required about eighteen hours. At the 
end of one and one-half days the Portland cements still remained 



Art. 7.] TESTS OF TENSILE STRENGTH. 19 

above the temperature of the room, but the natural cements had 
nearly returned to the temperature of the room. The cements 
which reached the highest temperatures almost invariably showed 
the sharpest crests in the curves which were plotted with the 
times and temperatures as ordinates. 

It is probably merely a matter of coincidence that the highest 
temperatures belonged to cements showing the highest ultimate 
compressive resistance, but it may be interesting to investigate 
this point more fully at some future time. The difference be- 
tween the Portland and natural cements is yery marked, but may 
be due partly to the excess of water used in mixing the samples. 

Temperature changes are naturally less marked when a cement 
is mixed with sand and stone than when neat, but they are still 
very noticeable. Experiments regarding these changes are now 
in progress on sqme large pieces of concrete work, but the results 
are not yet public. 

Art. 7. — Tests of Tensile Strength. 

The test of the tensile strength of a cement is the decisive test 
in regard to its acceptance for use, even though in the majority 
of building operations it is not the tensile strength, but the 
crushing strength of the material, which is desired. It may be 
shown, however, that these two resistances bear an almost fixed 
ratio to one another, and since the tensile tests are more easily 
made and require less expensive apparatus, they have practically 
displaced the crushing tests. 

The tests are made on small briquettes of standard form whose 
minimum area of cross-section is one square inch; these bri- 
quettes are formed both from the neat cement and from mixtures 
of the cement with various percentages of standard or normal 
sand, and they are tested at stated periods after making. The 
periods are usually one, seven and twenty-eight days. 

The tests which are made to determine the tensile strength of 
cement have often been criticised on account of the poor form of 
cross-section of the briquette, and on account of the use of a class 
of sand which is never employed in practice. Although errone- 
ous values of the actual strength of the cement in working prac- 



20 



PHYSICAL TESTS OF CEMENTS. 



[Ch. II. 



tice are thus found, a standard of comparison between different 
cements is still obtained. 

It is unnecessary to describe* any of the apparatus or any de- 
tails of the methods of operation. The following figures and 
tables are of interest as showing characteristic results of tests 
made on the tensile strength of various kinds of cement, and are 
given for the purpose of determining a point in the life of a 
cement when its strength ceases to show an increase at an ap- 
preciable rate. 

TABLE I. 

TENSION EXPERIMENTS 





1 Cement 
Sand 


1 Cement 
Sand 


1 Cement 
3 Sand 


1 Cement 
3 Sand 


1 Cement 
5 Sand 


1 Cement 
5 Sand 


Age 


Immersed 


Not 
Immersed 


Immersed 


Not 
Immersed 


Immersed 


Not 
Immersed 




Ultimate Resistance in Pounds per Sauare Foot. 


7 days 


515 
658 
697 
814 
765 
838 


642 
651 
600 
638 
575 
507 


277 

350 
457 
487 
550 
503 


301 
438 
538 
605 
703 
650 


127 
180 
233 
281 
271 
270 


131 

247 
335 
410 
442 
408 


28 days 

84 days 

6 months 

I vcar 


2 years 


Gauged with . . . 


23% 


10.1% 


9-5% water 



COMPRESSION EXPERIMENTS 



7 days . . . 
28 days- • 
84 days . . 
6 months. 

1 year . . . 

2 years . . 



6320 


6200 


2570 


2930 


I2I0 


8400 


8050 


3520 


4360 


1560 


II 200 


9700 


5100 


5750 


I9I0 


13000 


12200 


5280 


6160 


2150 


I4I80 


14200 


6520 


7720 


2150 


14700 


14800 


6000 


7100 


2450 



1260 
196,0 
3310 
3200 
3560 
3500 



Table I. shows the results of two sets of experiments made at 
the Laboratory de I'Ecole des Fonts et Chaussees, under date of 
February 6, 1896, and pubUshed by Berger & Guillerme in "Ci- 
ment Arme." The values given are all the mean of five or six 
specimens. 

In the first series of experiments the briquettes were exposed 
to damp air for twenty-four hours and then immersed in fresh 
water; in the second series there was no immersion. The cross- 



^See Appendix. 



Art. 7.] 



TESTS OF TENSILE STRENGH. 



21 



section of the specimens varied from 0.78 to 1.2 square inches. 
The lower part of the table is inserted to show the ratio between 
tensile and compressive stresses for mixtures of the same kind. 

Figure i was plotted from results published by E. C. Clarke, in 
Vol. XIV., 1885, of the Transactions of the American Society of 
Civil Engineers, and shows the strength obtained by Portland 
and natural cement and mortar briquettes whose minimum area 
of cross-section was 2J square inches. Twenty different brands 




12 Months 



FIG. 1.— CLARKE'S TESTS. 

of cement were used, and the figure represents 25,000 breakings. 
The ordinary cement briquette has a minimum area of i square 
inch, but comparative tests made at the time showed little dif- 
ference in result between cross-sections of i and 2J square inches. 
Figure 2 shows the results obtained in tensile tests on four 
brands of Portland cement, as published in the report for 1895 of 
M. L. Holman, Water Commissioner of St. Louis; each plotted 
point represents an average of ten briquettes. The briquettes 
were all i cement to 3 normal sand and were left one day in air 



22 



PHYSICAL TESTS OF CEMENTS, 



[Ch. II. 



and the remainder of the time in water. The figure shows a 
continual increase in the strength of the briquettes for the period 



600 



'400 



;3oo 



:2oo 



1 100 















































































































































































































































































■3 Sa 


1(1 
















< 










iCeu 


aent .- 






> 


















> 


, ■ 






- 


__^_^_ 


, 
















< 
< 
















/I 





^^^ 


: 


11 


^ 


, 


















/^ 








ii 




















< 


'if 


_^ 


^^^ 




f 
























^^ 


r^ 































































































































































6 Months 1 Year 



2 Years 



3 Years 



ZX Years 



Age of Specimens. 
FIG. 2.— HOLMAN'S TESTS. 



of 3f years shown; but a similar series of tests made upon neat 
cement briquettes showed a slight decrease after the end of one 



600 



300 



,2 100 -v= 







X- ^^ 


t— 


x^**^ 


\A 


^^^ 


1:6 _^ 


1:8 


V.Vi 



1 Month 



1 Year 
Age of Specimens. 
FIG. 3.— CLARKE'S TESTS. 



2 Years 



year, the greatest decrease, as compared to the maximum strength 
obtained, being about 20 per cent. It is only proper to note that 



Art. 7.] 



TESTS OF TENSILE STRENGTH, 



23 















































700 


























































Nea 


X 






-^ 






— ^ 




















I— -^ 


^ 


-— 


' 
































d< 




/ 








































R^OO 


> 


y 
























— 


— ' 














5 
















1:1 




































^ 


'-' 


^ 










/ 




— 


' 














si 

"Sa 

c 

Isoo 

CQ 






y 


V 








1:3 






y 
























/ 


r 






A 


' — 






y 
























•t 




f-^ 


^ 


^ 


































»200 


■* 


/; 


r^ 


^ 




1:4, 


.^ 


^ 






























// 


e-^ 






1:5 
































100 


> 


/ 


^--^ 


' 



























































































































2 3 1 

Age in Months 

FIG. 4— RAFTER'S TESTS. 



briquettes, when one year old or 
over, become very brittle and may 
show erratic results in the testing 
machine. 

Figure 3 shows the results ob- 
tained by E, C. Clarke, as part of the 
same experiments mentioned pre- 
viously, in which he found the varia- 
tion in the strength of cements when 
mixed with increased proportions of 
sand. These tests were all made on 
one single brand of cement and rep- 
resented 500 breakings. 

Figure 4 shows the strength at- 
tained by a Portland cement both at 
various ages and when mixed with 
different volumes of sand. Each 
point marked on the curves repre- 
sents an average of five briquettes. 
These tests were made by Mr. 




100 200 300 

Age in Days. 

FIG. 5. 



24 



PHYSICAL TESTS OF CEMENTS, 



[Ch. II. 



George W. Rafter and are published in the annual report of the 
"State Engineer of New York" for 1894. 

Figure 5 is taken from Johnson's ''Materials of Construction/' 
page 575, and shows the average tensile strength acquired at 
various ages by many samples of one brand of American Port- 
land cement, as reported by Messrs. R. W. Hunt & Co. 

R. W. Lesley published in the Journal of the Association of 
Engineering Societies, 1895, the results of long time tests made 
on samples of cement representing 300,000 barrels of the Giant 




1 Year 



2 Years 3 4 

Age of Specimen in Years 

FIG. 6.— LESLEY'S TESTS. 



Portland brand of cement. Figure 6 is plotted from these results, 
and represents a series of tests made on 50,000 barrels of cement 
used on the Sodom and Bog Brook dams of the New York aque- 
duct. The results there shown are characteristic of the entire 
series. Each point plotted is an average of 1,000 to 1,300 bri- 
quettes. Taking only the tests made on briquettes of one cement 
to three sand, it will be seen that the strength at three months 
and six months, as compared to five years, are respectively 60 per 



Art. 7.] 



TESTS OF TENSILE STRENGTH. 



25 



cent, and 73 per cent.; and for three months and six months, as 
compared to one year, respectively ^2, per cent, and 100 per cent. 
Figure 7 shows the results of experiments recorded by J. 
Grant in the Proceedings of the Institution of Civil Engineers, 
Vol. XXXIL, page 280, and shows the variation in the tensile 
strength of Portland cement briquettes from observations extend- 
ing over a considerable number of years. The form of specimen 
used was not the standard form as used to-day, the minimum 
area of cross-section being 2J square inches. The specimens 
were all kept in water from the time of making until the time of 
testing, and ten specimens were tested at each age. It will be 



2 ® 

o si 



a ® 





^^_^.l 






Portland Cement Neat 






• 


■ 


/ 


Pn 


rtlund 


Oo.tiveti^ 


1 : Thames i 

r y ii 


sand 1^ 




,^ 
















I 

















ICOO 



1200 



800 



iOO 



1 2 3 i 5 6 7 

Age in Years 

FIG. 7.— GRANT'S TESTS. 

seen that there is no increase of strength after two years. For 
neat specimens the percentage of increase gained after three 
months' age is 20 per cent., as compared to the final strength; 
and for the one cement to one sand mortar the corresponding 
percentage is 33. Similarly, comparing the increase in strength 
after six months to the final strength, these percentages become 
respectively 11 and 22. 

The following table shows the tensile strength of the Edison 
Portland Cement Company's cement, and is inserted as a matter 
of interest as giving the tensile resistance of the latest cement on 
the American market; the tests are taken from the report already 
mentioned. 

■ Neat, I day =325 lbs. per sq. in. Average of 5 specimens. 
Neat, 7 days=676 lbs. per sq. in. " " " 

1:3, 7 days=255 lbs. per sq. in. 
1:3, 28 days=33I.lbs. per sq. in. 



26 PHYSICAL TESTS OF CEMENTS. [Ch. II. 

In all these figures it is seen that cement and the cement mix- 
tures attain a strength not differing greatly from the ultimate 
strength within a period of three months from the time of set- 
ting, and practically that within a month or so after this period 
no appreciable change in the strength takes place. 

It is important to recognize this fact in order to appreciate 
that it will make no sensible difference in tests of cement mix- 
tures when the age of the specimen is in the neighborhood of 
three months. The results so obtained need no correction for 
age and will all be comparable. 

It is of interest to record the following empirical formula which 
has been proposed by W. C. Unwin (Proc. Inst. Civ. Eng., Vol. 
LXXXIV.) for determining the tensile strength of a briquette 
within two years after making; he derived it by analyzing the re- 
sults of tests by Bauschinger, Grant, Clarke and others. 

If 7 is the strength of a cement or mortar at x weeks after mix- 
ing, and a the strength of the same in pounds per square inch at 
seven days, then 

y=^a-\-b {x — i)^ 

The constant n has values which can be assigned beforehand, 
and the constant b is determined by experiment on pieces more 
than one week old. Unwin, assuming for the case of tension 
n to be J, finds that b varies within rather narrow limits. 

Art. 8. — Ratio of Compressive and Tensile Strengths. 

The ratio of compressive and tensile strength is not a constant 
quantity for all ages of a mortar, since, in general, compressive 
strength increases faster than the tensile strength; but experi- 
ments show that the variation of this ratio is not very great. 

J. B. Johnson in "Materials of Construction" analyzes the re- 
sults of numerous experiments on a mortar of one cement to 
three sand, which were recorded by Tetmajer in his "Comrnuni- 
cations," Vol. VI., and expresses the ratio between these strengths 
by the following equation : 

2^=^8.64-^-1.8 log A 

where R represents the ratio between the compressive strength 



Art. 8.] 



RATIO OF COMPRESSION TO TENSION. 



27 



and the tensile strength, and A is the age of the cement mortar in 
months. 

Biising and Schumann, in "Der Portland Cement," 1899, pre- 
sent in Table I. results which furnish the relations between these 
two kinds of stress. The specimens were made with ordinary 
sand and gauged with different percentages of water, and were 

TABLE I. 





1 Per Cent. Water 


1 2 per Cent. Water 


15 per Cent, Water 


Age 
in 


Pounds per Sq. In. 


Ratio 


Pounds per Sq. In. 


Ratio 


Pounds per Sq. In. 




Days. 


Tension 


Com- 
pression 


Tension 


Com- 
pression 


Tension 


Com- 
pression 


Ratio 


7 

28 

90 

180 


284 
370 
407 
456 


2860 
4050 
5050 
5400 


10. 1 
10.9 
12.4 
II. 8 


196 
326 
366 
380 


1550 
2270 
2940 
3200 


7.8 
7.0 
8.0 
8.4 


143 
260 
328 
321 


781 
1420 
2130 
2410 


5.4 
5.5 
6.5 
7.5 



tested at various ages. It is to be noted that with the increase 
of water the compression decreases faster than the tension, and 
that with the increase of age the compression tends to resume its 
former relations. 

TABLE IL 







Tension 


Compression 


Bending 


Shear 




Ult. Resistance 


Ult. Resistance 


Extreme Fibre 


Ult. Resistance 






Pounds pep 


Pounds per 


Stress in Lbs. 


Pounds per 


Age in Weeks 


Mixture 


Square Inch 


Square Inch 


per Sq. Inch 


Square Inch 






Specimens F 


lardened in 






Air 


Water 


Air 


Water 


Air 


Water 


Air 


Water 


r 


1:0 


231 


224 


I860 


I9IO 


695 


625 


276 


271 


I \ 


1:3 


106 


95 


920 


880 


273 


247 


109 


116 


I 


1:5 


68 


64 


543 


537 


168 


158 


81 


77 


r 


1:0 


266 


294 


246O 


2490 


860 


887 


3I6 


346 


4 { 


1:3 


148 


169 


1500 


1040 


392 


381 


182 


181 


\ 


1:5 


119 


103 


962 


977 


284 


276 


136 


131 


f 


1:0 


257 


292 


3400 


4680 


lOIO 


1350 


388 


415 


104 to 113. S 


1:3 


244 


272 


2080 


3340 


748 


973 


294 


375 


I 


1:5 


177 


232 


I5IO 


2960 


545 


810 


248 


364 



An exceedingly interesting set of experiments was published 
as long ago as 1879, t>y Bauschinger, in the Proceedings of the 
Munich Technical Institute. Bauschinger experimented on mor- 
tar specimens of i cement to o sand, i cement to 3 sand, and i ce- 



28 



PHYSICAL TESTS OF CEMENTS. 



[Ch. II. 



ment to 5 sand. His tension specimens had a cross-section of 
2.4X4-8 ins. ^11. 1 sq. ins. The compression specimens were 
cubes 4.8 inches on the side, and his flexure tests were made on 
specimens 2.4X4.8X12 inches long, tested with a span of 10 
inches. The 4.8 inch side was vertical. Tests of the shearing 
resistance were made on the flexure specimens. 

Table 11. shows results of all these tests, each value shown 
being an average of 9. 

The extreme limits of the ratio of compression and tension 
will be found between 13.2 and 8.00 for dry specimens, and 16.02 
to 7.35 for the wet. It is to be noted, however, that this value 
of 16.02 was exceptional, the next highest ratio being 12.76. 
The limiits of the ratios of the ultimate fibre stress in flexure to 
maximum tensile stress were 3.93 to 2.46 for the dry, and 4.65 to 
2.25 for the wet. The limits of the ratios between shear and ten- 
sion were 1.5 1 to 1.03 and 1.57 to 1.07 for the dry and wet re- 
spectively. 

TABLE III. 







Gauged with 
20 per Cent. Water 


Gauged with 
22 per Cent. Water 


Gauged with 
25 per Cent. Water 


Age in 


Compressive 
Strength in 
Lbs. per Sq.In. 


Tensile 
Strength in 
Lbs. perSq.In. 


Ratio 


Compressive 
Strength in 
Lbs. per Sq.In. 


Tensile 
Strength in 
Lbs. perSq.In. 


Ratio 


Compressive 
Strength in 
Lbs. perSq.In. 


Tensile 
Strength in 
Lbs. perSq.In. 


Ratio 


Air. 


Water. 




Days. 


Days. 




I 

7 

28 

I 

I 




717 
3040 
3990 
4250 
7370 


196 
354 
566 
780 
906 


3.7 
8.6 
7.1 

5.5 
8.1 


595 
3260 
3760 
4720 
6870 


189 
392 

457 
666 
866 


3.1 

8.3 
8.2 
5.8 
7.9 


430 
2610 
3130 
3880 
7580 


190 
402 
450 
329 
758 


2.3 

6.5 

7.0 

II. 8 

1 0.0 






6 
27 



Table IIL furnishes values of the ratio between tensile and 
compressive stresses, and is taken from the Watertown Arsenal 
Report for 1902. The specimens were all of neat Peninsular 
Portland cement. Ten specimens of each kind were tested, with 
varying percentages of water and at different ages. The ratios 
of the two kinds of stress are given in the table. The tensile 
specimens were of the standard form; although not so stated, it 
is probable that the crushing tests were made on the broken 
halves of the tensile specimens. 



Art. 9.] VARIATIONS IN THE MAKING OF TENSILE TESTS. 29 

Reviewing all these experiments, it is seen that it will never 
be far from wrong to assume the ratio between ultimate com- 
pression and tensile resistances as about lo; although it should 
be noted that all the tensile tests were made on specimens of a 
form which probably give too high values. 

Art. 9. — Variations in the Making of Tensile Tests. 

The author does not believe it to be of any importance to con- 
sider in any detail questions bearing on variations in the manner 
of making tensile tests. Under this heading may be included 
the variation in the rate of loading a specimen; the testing of a 
specimen, either dry or wet, or an appreciable length of tim^e 
after taken from the storage tanks; the variations in the strength 
due to mixing with dififerent percentages of water; the effect of 
temperature changes of the water in the immersing tanks; the 
effect of salt water in these tanks; the period elapsing before 
placing the briquettes in water after making, whether twenty- 
four hours or immediately upon setting hard; the methods of 
filling the moulds, whether by ramming or by slightly tamping; 
the time em.ployed in mixing the materials in the dry state or in 
the wet state; the eccentricity of a specimen in the clips of the 
testing machine; the filling of the molds with dry cement, and 
then adding water, etc. 

The results of the tensile tests are made simply a basis of com- 
parison for accepting or rejecting offered cements, and although 
the questions noted do affect the results appreciably, under 
standard conditions of making, the personal equation of the 
operator will be a factor of greater importance than anything 
else. Certain points depending on comparative results may, 
however, be determined in the tensile tests of briquettes, of 
which the following is the most important, namely, the advan- 
tages to be gained by the use of one of several possible sands. 
A choice between different sands offered may be determined by 
these tensile tests, and this question frequently arises in building 
operations. In this connection there has lately been much ques- 
tion concerning the suitability of rock screenings for use in place 
of sand. 



30 PHYSICAL TESTS OF CEMENTS, 

Art. 10.— Variations of Sands in Tensile Tests. 



[Ch. 11. 



The following experiments, reported by E. S. Wheeler in 
the Report of the Chief of Engineers, U. S. Army, for 1894, 
page 2321, bear directly upon this point. Table I. shows the 
mean tensile strength attained by various mixtures of natural 
sand, of the standard sand used for testing and of various rock 
screenings with natural cements; each result shown is an aver- 
age of five to ten specimens, all briquettes being one cement 
to three sand. The sands were all brought to the same degree 
of fineness by sifting and remixing, there being used, in all 
cases, excepting for the standard sand, 25 per cent, each of sand 
retained between sieves Nos. 20 to 30, 30 to 40, 40 to 50 and 50 
to 80. The superiority of the mixtures formed from screenings 
obtained from crushed limestone and sandstone is clearly shown. 
The table is for natural cements only; but Portland cements fur- 
nished exactly similar results. 

TABLE I. 



Kind of Sand 


Mean Tensile Strength in Lbs. Per Square Inch at Age of 


28 Days 


6 Months 


1 Year 


2 Years 


Crushed Quartz 

Point aux Pins Natural Sand . 

Limestone Screenings 

Sandstone Screenings 

Standard Sand 


117 
93 
162 
113 
118 


344 
297 
467 
316 
330 


356 
339 
526 
416 
342 


332 
308 
601 
462 
324 







The same experimenter records on page 2806 of the Report of 
the Chief of Engineers, U. S. Army, for 1896, experiments made 
in determining the tensile resistance of briquettes when mixed 
with natural sand of varying fineness. The sand was Point aux 
Pins, and each result in Table II. is an average of five briquettes, 
the briquettes being one cement to two sand. Portland cement 
was used. The exponents of the letters C, M, F and V show the 
percentages of each fineness used, C being the material passing 
the No. 10 sieve, V passing the No. 40 sieve, M being the ma- 
terial retained between the 20 to 30 sieves, and F between the 30 
to 40 sieves. The results obtained are very interesting. They 
show that the mortar in which the sand contains the greatest 



Art. 10.] 



VARIATIONS OF SANDS IN TENSILE TESTS. 



31 



variations in the sizes of grain attains the greatest strength. This 
is in perfect accord with the opinion that the balancing of the 
material in a mortar is of the utmost importance. 

TABLE II. 



Fineness 


Tensile Strength in Pounds per Square Inch at Age of 


28 Days 


6 Months 


1 Year 


2 Years. 


Mw F" yo 

M* F^ V^ 
M2 F* V* 
Ml F=* V« 
Ml F2 V^ 

Qo M^o F^^ V^** 
Qo M-° F^° V^^ 

Qo f^Vo p35 Y45 
Q5 M^S p30 V^" 

Qo Ml" F^^ V^** 


342 
300 
290 
246 
271 


471 
448 
425 
384 
366 

566 
544 
551 
528 
540 


560 

515 
494 
455 
456 

18 Months 
581 
592 
585 
589 
593 


591 
507 
503 
442 
438 
3 Years 
632 
622 
587 
629 
622 



Exponents of letters C, M, F, V show numbers of parts of each degree of fineness used; C 
passes No. 10 sieve; M, between Nos. 20 to 30; F, between Nos. 30 to 40; V passes No. 40. 

Figure i is taken from tests reported by R. Feret in the "An- 
nales des Fonts et Chaussees," 1892, and shows the ultimate com- 
pressive resistance attained by various mortars mixed with vari- 



- 


/ 
















^^ 


^ 












y 


^ 


[? 


/^ 




* 


2840 Lbs. 








/ 


/I 


/ 


/ 








per sq. in. 








J/ 


/ 


?7 


/ 










1420 Lbs. 
per sq. in. 




i 


V 


f\ 


'' 














<^T 


/ 


/ 
















/ 


^ 


/ 

















Cement .0 .1 .2 .3 .4 .5 .6 .7 

Sand 1.0 .9 .8 .7 .6 .5 .4 .3 

Parts of Sand and Cement 

FIG. 1.— FERErS TESTS. 



1.0 
.0 



ous proportions of the same cement to two kinds of sand, the 
relations varying from neat to 1 19. The specimens were im- 
mersed two months in sea water, and two kinds of sand were 



32 



PHYSICAL TESTS OF CEMENTS. 



[Ch. II. 



used — one, which was marked "Q," was very coarse sand; the 
other, marked "P," very fine. It will be seen that the coarse 
sand gave uniformly higher resistance than the fine. 

Table III. is taken from a paper by E. S. Larned, presented 
before the American Society for Testing Materials, 1903, and 
shows the tensile strength of cement mortar with sand grains of 
different diameters. Each result shown is an average of six 
briquettes. The table gives only the results for Giant Portland 
cement mortar, one part cement to two of sand by weight, but the 









TABLE 


III. 








Percentage 


: of Sand Used 


Ultimate Tensile Strength a 


t the Age of 


No. 30 


No. 20 


No. 100 


Fine 


7 Days 


28 Days 


6 Months 


100 








286 


288 


412 




100 






294 


331 


473 






100 




201 


226 


294 








100 


129 


159 


223 


80 


10 


10 




361 


380 


486 


70 


15 


nyz 


2% 


301 


303 


428 


60 


20 


15 


5 


307 


311 


419 


50 


25 


n'A 


7>^ 


391 


400 


538 


40 


30 


20 


10 


350 


355 


475 


30 


25 


30 


15 


362 


359 


478 


20 


20 


40 


20 


317 


374 


480 


10 


15 


50 


25 


291 


354 


488 


50 






50 


247 


287 


351 


50 


50 






440 


408 


542 


50 




50 




309 


336 


438 


25 


25 
Crushed 


25 

Quartz 


25 


279 


337 


447 
3 Months 


40 





60 




257 


331 


351 



Natural sand used : first passed through No. 8 screen and residue excluded ; No. 30 sand 
passed No. 20 screen and caught on No. 30 screen; No. 20 sand passed No. 8 screen and 
caught on No. 20 screen ; No. 100 sand passed No. 30 screen and caught on No. 100 screen. 
Fine is clean white sand sifted through No. 100 screen. 



original paper shows similar results with tests upon two natural 
cements. All the briquettes were gauged with the same per- 
centage of water. It will again be noticed that those briquettes 
in which the sand is composed of varying percentages of the dif- 
ferent kinds show" uniformly greater strength than those bri- 
quettes formed of one kind of sand only. In those briquettes in 
which one grade of fineness of sand only is used the coarsest 
sand shows the highest ultimate strength. 



Art. 10.] VARIATIONS OF SANDS IN TENSILE TESTS, 



33 



R. Feret records, in the "Annales des Fonts et Chaussees/' 
1892, a series of tensile tests on 1 13 mortar in which the cements, 
in all cases, were the same, but the sand was composed of many 
different materials. These materials were used either neat with 
the cement or in combination with each other. Among the ma- 
terials were porphyry, granite, marble, chalk, quartzite, broken 
glass, crushed brick, charcoal, sawdust, mica, etc. All speci- 
mens were treated exactly alike and were kept in sea water for 
various periods of time up to one year. Of all these materials, 
it was found, at the end of a year, that the 1 13 marble mortar 
gave the highest ultimate tensile resistance, and that the granite, 
quartz and mica mixtures furnished values considerably less. 
The actual values obtained by these mixtures are not of much 
importance; but it is interesting to record Feret's results on 
marble, since they substantiate the claim that a calcareous stone 
yields stronger concretes than a quartz or granite stone. 

TABLE IV. 



Material 


Proportion of Sand 
to Cement by 


Ult. Tensile Resistance in Lbs. per Sq. In. 
at the Age of 




Volume 


1 Day 


7 Days 


28 Days 


Cow Bay Sand 

Fine Screenings 

Sand from Reservoir. . 

Cow Bay Sand 

Fine Screenings 

Sand from Reservoir. . . 


2 
2 
2 
3 
3 
3 




107 
92 
86 
37 
39 
29 


364 
330 
175 
228 
223 
122 


530 

528 


311 
394 





In connection with this it is of interest to note that in "Engi- 
neering News," May 17, 1890, is given an abstract of results ob- 
tained by breaking a large number of cement blocks 3 feet 3I 
inches long and 7.9 inches square, the original tests having been 
recorded in "Wochenschrift des Oester. Ing. Ver." Sufificient de- 
tails are not provided to permit an analysis of the results as flex- 
ure tests, but the following general statement is worth recording: 
That the strength of specimens made with granite, with clinkers 
(vitrified brick) and with sandstone varied in the order named, 
granite showing the greatest strength. 

Table IV. is taken from a report made by Mr. A. Black, of 
the Department of Civil Engineering of Columbia University, to 



34 



PHYSICAL TESTS OF CEMENTS, 



[Ch. II. 



the Investigating Commission on the Jerome Park Reservoir, 
1903, and shows the tensile strength of three kinds of mortars 
mixed with Atlas Portland cement. The sand for these mix- 
tures was either natural Cow Bay sand, or the natural sand 
from the site of the Jerome Park Reservoir, or artificial sand 
composed of rock screenings. Each figure is the average of a 
large number of briquettes, and it is seen that the briquettes 
made with the screenings are not inferior to those briquettes 
made from the natural sand. 

Table V. shows the relative strength of sand and stone dust 
mortars, as determined by T. S. Clarke, and as reported by him 
in the "Engineering News" of July 24, 1902. In his case, how- 
ever, the stone dust was very much finer than the sand, and the 

TABLE V. 
Showing Strength of Sand Mortar Compared with Stone Dust Mortar; 
Portland Cement; 24 Hours in Air, 6 Days in Water; Amount of 
Water Used, 10%. 



Proportions 


Av'ge Tensile Strength, 
Lbs. per Sq. In. 


Average Number 


Cement 


Sand 


Stone Dust 


of Tests 


I 
I 
I 
I 


2 
3 


2 
3 


245 
345 
216 
241 


15 

16 

3 

3 



results show that the tensile strength of the natural sand mortar 
is greater than that of the stone dust mortar. This is to be ex- 
pected, if the fineness of the two varieties exhibits the difference 
noted. 

Reviewing the preceding experiments, it may be concluded 
that rock screenings may be substituted for sand, either in mor- 
tar or concrete, without any loss of strength resulting. This is 
important commercially, for it precludes the necessity of screen- 
ing the dust from crushed rock and avoids, at the same time, the 
cost of procuring a natural sand to take its place. 

Effect of Clay in Sand — In construction work the question of 
the presence of fine clay in a natural sand is generally at once dis- 
posed of by prohibiting it, but the following data show that this 
solution is not satisfactory. ' : - 



Art. 10.] 



EFFECT OF CLAY IN SAND. 



35 



Table VI. is taken from Vol. XIV. of the Transactions of the 
American Society of Civil Engineers, 1885, in which are re- 
corded experiments made by E. C. Clarke concerning the adul- 
teration of sand with clay. It will be seen that mixtures of clay 
and cement without the addition of sand have no permanent 
strength ; but the presence of clay in moderate amounts does not 
weaken cement mixtures. Each figure in the table represents 
the average ultimate tensile resistance in pounds per square inch 
of fifteen briquettes made from Portland cement, but experiments 
made with the natural cements furnished similar results. 

G. J. Griesenauer has reported in ''Engineering News," April 
28, 1904, tests made on the tensile strength of Portland and 
natural cement mixtures when the sand which was used con- 
tained various percentages of clay or loam; also, when the sand 
was natural dirty sand, just as it came from the sand bank, and 

TABLE VI. 



Age 


Cement 2 
Clay 1 


Cement 1 
Clay 1 


Cement 1 
Sand 2 


Cement 1 

Sand 2 

Clay 0.2 


Cement 1 

Sand 2 

Clay 0.4 


Cement 1 

Sand 2 

Clay 0.6 


I Week 

I Month 

6 Months 

I Year 


185 

263 
248 
303 


192 
271 
322 
301 


150 
186 
320 
340 


197 
253 
361 
367 


185 
245 
368 
401 


145 

203 
317 

384 



when the same was washed. The experiments extended over a 
considerable period of time. 

Two sets of experiments (which it is unnecessary to repro- 
duce here) were made on Portland cement mortars i :2 and 1 13, in 
which loam was added to the clean sand in percentages as high 
even as 20 per cent. The results from those tests show that the 
clay afifected, in almost all cases, the i :2 mortars adversely, but 
appeared, on the contrary, to benefit the 1 13 mixtures for almost 
every percentage of loam added and for all ages. These con- 
tradictory results are probably explained by the fact that in the 
one case the loam helped to balance the mixture, and in the other 
case not. 

Figures 2 and 3, from the same tests, are, however, of greater 
interest, since they represent more nearly conditions in practice. 
Figure 2 shows the strength of 1:3 Portland cement mortars 



36 



PHYSICAL TESTS OF CEMENTS. 



[Ch. II. 



mixed with natural sand taken from various pits and containing 
the percentages of loam indicated. Figure 3 shows the results 
obtained on i : 3 mortars in which the sand containing 6 per cent, 
of loam was first used in its natural condition and then after hav- 
ing been washed. 

The results are entirely harmonious. They show that the 
presence of loam in a 1 13 mortar rarely decreases the ultimate 



Age 



700 
650 

600 

d 

"!! 560 

m 

o, 500 















Xpj 


It Povrlq 


mH 


'em( 






.^ 


^^ 


^ 








^ 


—- 





"" 






—■ ~~ 


iUt 


'^' 












1 
1 
1 


r 











































































































450. 
400 
350 


























^ ._ 





— 


— 


— 


- 














^iiT^Y^ 


" 




^ -^ 


bji. 




'^. 


.'-■ 










-^' 


.^^' 


,^'^ 


3,2i2i?Ji^'- 




^ 


^— 


"5.2^ Lo'am 


— 


— "^ 




900 
250 
200 
150 
100 




-^ 












^' 




,^r* 


^ 


^ 


f^' 


9 


.2.15 


... 
Loam 










.- 


— — 


— - 


/ 
/ 


/ 




9^ 


.'" 


^J^- 


... 


.... 






.__ 


._. 


"' 












i 


^; 


y 
































y 












- 


\ 
































1 


[ests 


Of It 

fron 


3 Mo 
iDifl 


rtar 
'eren 


witL 
tPit 


San< 


L 













FIG. 2.— TESTS BY GRIESENAUER. 

strength. As has already been said, the reason for this is prob- 
ably to be explained by the better balancing of the mixture. 
Nothing indicates why this same reasoning may not apply as 
well to mixtures of cement, sand and stone. If this be the case, 
there is no reason why a loamy sand should not be used for 
making concrete. 

Professor C. E. Sherman has also recorded in the "Engineer- 
ing News" of November 19, 1903, an extended series of tests 
which he had made concerning the effect of clay and loam on 
cement mortars. The tests were made on the usual form of ten- 



Art. 10] 



EFFECT OF CLAY IN SAND. 



37 



sile briquette, with three different kinds of sand, lake, bank and 
crushed quartz, each of which was artificially mixed with varying 
percentages of clay and loam up to 1 5 per cent. Five specimens 
of every mixture, and with two different brands of Portland 
cement, were tested at ages varying between one week and one 
year. The uniformity of the results is such that it seems un- 
necessary to give in detail any of the experiments, since only 
five curves out of seventy-two, representing the tensile strength 



/ 



850 



800 



750 



70»/ 



J 650 






iOO 



I 350 

tn 

^ 300 

c 

^. 250 



150 



100 

























y^ 


















M 


>y 


^' 






<<>,^ 

> 


^-' 


\t 


l^th 


-t 






'^y 








/ 
/ 
/ 




























































( 


$U- 


am 


n Sj 


nd 











r^ 


^^ 


y^' 












>A\ 




J 




y' 






-\0_ 


^■$ 


■}^- 


.^i^ 


> 


/ 


,^^' 






~^— 












"" 






1 
/ 


>•''' 






















' 










L ,. 















Tests of la Mortar with 67cLoamy Saud 
and with game Sand Washed 

FIG. 3.— TESTS BY GRIESENAUER. 



of a mortar composed of sand with clay or loam, fell below the 
curves representing the tensile strength of the clean sand mortar. 
And in eight cases out of twelve the 15 per cent, mixtures fur- 
nished the very highest results at the end of one year. 

Table VII. shows results abstracted by the ''Engineering 
Record," July 16, 1904, from tests describel by Charles M. Mills 
in a paper read before the Philadelphia Engineers' Club. The 
tests were made in the laboratory of the Philadelphia Rapid 
Transit Commission on briquettes of the standard tensile form. 



38 



PHYSICAL TESTS OF CEMENTS, 



[Ch. II. 



The gravel used in the mortar tests after screening fulfilled the 
requirements for ''coarse sand or gravel, graded from coarse to 
fine, to reject all particles exceeding ^ inch in diameter," but it 
contained a considerable quantity of loam. Tests were made 
with the natural gravel, with the same screened, and with the 
same washed, as fully shown in the table, each result being the 
average of 4 to 6 specimens. 

The greatest strength was attained in the crushed rock mix- 
tures, and the lowest strength was given by the standard quartz 



TABLE VII. 



Material 



Percent- 
age of 
Loam in 
the Sand 



Percent- 
age of 
Water 

Used in 
Mixing 



Av. Tensile Strength 
in Lbs. per Sq. In. 



1 Day in 

Air 

6 Days in 

Water 



1 Day in 

Air 
27 Days 
in Water 



A — Neat Portland Cement 

B — Standard Quartz Sand • . . • 

I Cement to 3 Sand. 
C — Gravel (unwashed, unscreened) 

I Cement to 3 Gravel. 
D — Gravel (washed, unscreened) 

I Cement to 3 Gravel. 
E — Gravel (unwashed, screened) 

I Cement to 3 Gravel. 
F — Gravel (washed, screened) 

I Cement to 3 Gravel. 
G — Trap Rock Dust 

28% retained on Sieve No. 20. 

I Cement to 3 Grit. 
H — Trap Rock Grit 

I Cement to 3 Grit. 
J — Crushed Trap Rock 

I Cement to 3 Crushed Rock. 
K — Trap Rock Grit and Excavation ) 

Gravel (unwashed, screened) ) 

I Cement, l}4 Grit, l}4 Gravel. 



25 

3 
25.2 

3.2 
I6.4 

II.4 



21 
9.9 

II. 2 

10.7 

13.7 

II. 2 

15.0 

12.5 
II. 2 

12.5 



527 
175 

208 

230 

219 

211 

213 

282 
279 

218 



862 
263 

316 

355 
335 
367 
385 

459 
416 

372 



sand; these results might have been expected. In groups E to 
F, which contained the loamy gravel, the variation due to the 
different percentages of loam is seen to be practically negligible ; 
a very slight increase is shown for the clean gravel specimens at 
the end of 28 days. In the work for which these tests were a 
preliminary, a mixture of equal parts of crushed trap rock grit 
and screened gravel was used. 



Art. 1 1.] TEST OF CONSTANCY OF VOLUME. 39 

It appears, therefore, that the presence of a loam or clay in a 
sand may not be objectionable. 

Art. II. — Test of Constancy of Volume. 

Improperly made cements sometimes fail, even after a con- 
siderable period following the setting, by the checking or swell- 
ing of the cement, which in turn causes disintegration of the mor- 
tar. The object of the test of constancy of volume, therefore, is 
to endeavor to determine such qualities, if present, in as short a 
time as possible. 

The tests are made on small pats of cement, which may be 
treated in various ways, such as by immersion in hot water or in 
cold water or in chemical solutions; after a certain lapse of time 
they are then examined as to the presence of defects, such as 
distortion of the specimen or cracks. The hot water or chemical 
test, however, has never been considered entirely satisfactory, 
either for the purpose of accepting or rejecting a cement. The 
failure to pass the hot water test does not necessarily imply re- 
jection; it classes a cement as suspicious, but the appearance of 
defects in specimens left in cold water for periods of seven to 
fourteen days does determine its unfitness for use. 

It is proper to say, however, that sometimes freshly burned 
cements, which fail to pass the ''cold water" test, may pass the 
sam.e after some period of ''aging"; it is therefore possible that 
the same cement may be accepted at a later period after having 
been previously rejected. Quantitative results are not obtained 
in these tests. 



CHAPTER III. 
GENERAL PHYSICAL PROPERTIES. 

Before treating of the resistance to stress of cement mixtures 
the following physical properties will be considered: 

(a) The change in volume of cement mixtures when setting. 

(b) The coefficient of expansion due to temperature changes. 

(c) The action of sea water. 

(d) The porosity and impermeability of cement mixtures. 

(e) The effect of freezing. 

(f) The adhesion of iron rods to cement mixtures. 

(g) The fatigue of cement mixtures. 

Art. 12 — Variation in Volume of Cement Mortars 
in Air and Water. 

The general conclusions as to the variation of volume which 
takes place during the hardening of cement mixtures are prac- 
tically agreed upon by all experimenters; they have been well 
stated by Professor G. F. Swain, who made elaborate experiments 
upon the changes of dimensions during the setting of American 
cements at the Massachusetts Institute of Technology with the 
aid of two students. These tests are reported in the Trans- 
actions of the American Society of Civil Engineers for July, 
1887. Experiments were made upon several brands of natural 
and of Portland cement. Five-inch cubes were made, both of 
neat cement and with a mixture of one cement to one sand. In 
two cases mixtures of one cement and three sand were also 
made. One specimen of each pair of cubes was left in the air, 
the other in water. Observations were taken at intervals rang- 
ing from one day to twelve weeks, and the following conclusions 
were reached : 



Art. 12.] VARIATION IN VOLUME IN AIR AND WATER. 



41 



1. Cement mixtures hardening in air diminish in Hnear dimen- 
sions, at. least to the end of twelve weeks, and in most cases pro- 
gressively. 

2. Cement mixtures hardening in water increase in like man- 
ner, but to a less degree. 

3. The contractions and expansions are greatest in neat cement 
mortars. 

4. In general the quick setting cements show the greatest con- 
traction when neat, and the expansion of the quick setting ce- 
ments is also greater. 

5. The changes are less in mortars containing sand. 

6. The changes are less in water than in air. 

7. The contraction, at the end of twelve weeks, is 

For neat cement 0.14% to 0.32% 

For one cement to one sand. . 0.08% to 0.17% 

8. The expansion, at the end of twelve weeks, is 

For neat cement 0.04% to 0.25% 

For one cement to one sand. . 0.00% to 0.08% 

9. The contraction or expansion is essentially the same in all 
directions. 

Professor Bauschinger of Munich reported the results of simi- 
lar tests in "Mittheilungen aus dem Mechanisch-Technischen 
Laboratorium" of the Royal Technical Institute of Munich, Vol. 
VII., and his results confirm those of Professor Swain; his test 
specimens were cubes 4.72 inches on a side. The following table 
shows his result : 

TABLE I. 



Mixture 
Cement to Sand 


Age 


Contraction in Per Cent. 
Hardening in Air 


Expansion in Per Cent. 
Hardening Under Water 


Neat 
1:3 
1:5 


16 weeks 
16 weeks 
16 weeks 


.12 to .34 

.08 to .15 
.08 to .14 


.01 to .15 

to .02 

—0.03 to .02 



Similarly Mr. John Grant records in Vol. LXII., Proc, Inst. 
Civ. Eng., the results of his experiments on prisms four inches 
long and two inches square, hardening only in water. He finds 
that at the end of a year neat cements, without plaster of Paris, 



42 



GENERAL PHYSICAL PROPERTIES, 



[Ch. III. 



expand .09 to .21 of i per cent., and for one cement to three sand 
.01 to .06 of I per cent. These figures were increased for ce- 
ments with gypsum. 

Dr. C. Schumann, in his book, "Portland Cement," 1899, re- 
cords the results obtained by him in measuring the increase in 
volume for specimens 3.9 inches long with a cross-section of 
•775 sq. in., which were immersed in water for various periods 
of time. Table II. is abstracted from page 78 of this book; each 
value shown gives the average percentage of increase in length 
for ten specimens of each kind: 

TABLE II. 



Age in Weeks 


Neat Specimen 


1 Cement 
3 Normal Sand 


I 


.048% 

.082 

.104 

.125 

.139 

.146 


.015 
.021 


4 


13 


.024 


26 


.028 


39 

52 


.030 
.033 







M. Gary records in the Trans. Am, Soc. Civ. Eng. for October, 
1893, the results of some tests by Dr. Tornei, manager of the 
Stern Portland cement factory; the size of specimen was the 
same as used by Bauschinger. Table III. is an abstract, being 
the average of the first six cements there shown. 







TABLE III. 




Mixture 


Age in Days 


Percentage of Contraction, 
Hardening in Air 


Percentage of Expansion, 
Hardening Under Water 


Neat i 

I Cement \ J 
3 Sand . • j ' " * * | 


7 

28 
90 
7 
28 
90 


.064 
.129 
.181 
.018 
.033 
.089 


.014 
.026 
.021 
.Oil 
.018 
.028 



Considere has stated that the shrinkage of cement in air may 
vary from 0.15 to 0.2 per cent, for neat cement, and from 0.03 to 
0.05 per cent, for mortar poor in cement; and, similarly, he has 
found that pure cement swells under water from o.i to 0.2 per 
cent., and that concrete poor in cement swells from 0.02 to 0.05 



Art. 13.] THERMAL LINEAR EXPANSION. 43 

per cent. These figures show accordance with the preceding re- 
sults and may be adopted for use. 

The report of the Boston Transit Commission for the year 
ending August 15, 1901, records some measurements made by 
H. S. R. McCurdy on the shrinkage taking place in concrete 
after it has set. Two beams were used; the one kept in air was 
8 inches square and 8.9 feet long, and the other, whose size is 
not given, was kept in water. The conclusions reached were 
that the concrete hardened in air would shrink .028 per cent, in 
twelve weeks, and that the concrete in water would shrink two- 
thirds of this. 

The latter conclusion does not agree with results obtained by 
other experimenters, and probably little reliance should be placed 
upon these figures, since the apparatus used was crude and the 
number of tests was small. 

Art. 13. — The Coefficient of Expansion Due to 
Temperature Changes. 

The earliest work recorded concerning the linear thermic ex- 
pansion of concrete is due to Bouniceau, who published his re- 
sults in the "Annales des Fonts et Chaussees," 1863, page 178. 
His work was performed on rectangular prisms 65 to 94 mches 
long and about 7 inches on each side, the blocks being placed in 
water whose temperature varied from 10 to 95 degrees C. The 
apparatus used was checked by measuring the determined co- 
efficient of expansion for other materials. 

Bouniceau tested altogether ten blocks, either of solid stone, 
concrete, mortar or neat cement, the latter being in all cases 
Portland; the following are the results obtained on the cement 
mixtures : 

Neat Portland cement 00000594 per degree F. 

One cement to two silicious sand 00000655 " '' " 

Concrete (proportions not given) (stone 

being silicious gravel) 00000795 " " " 

Professor W. D. Pence of Purdue University has made a 
series of investigations, the results of which are given in a paper 
of the Western Society of Engineers, November, 1901. He 



44 



GENERAL PHYSICAL PROPERTIES, 



[Ch. III. 



made experiments on Portland cement concretes of the composi- 
tions shown in the following table. The values there given show 
the coefficient of linear expansion per degree Fahrenheit. 

TABLE I. 



Kind of Concrete 


Coefficient of Expansion 


1 Cement ] 

2 Sand > 

4 Broken Stone J 


.0000055 


1 Cement i 

2 Sand \ 

4 Gravel J 


.0000054 






I Cement 1 




5 Gravel J 


.0000053 



The method of conducting these experiments involved the 
comparison of the concrete bars with metal bars, and the results 
obtained may perhaps be regarded with some suspicion on this 
account. Busing and Schumann, in ''Portland Cement," page 
yy, quote Meier as giving the coefficient of expansion of neat 
cement between — 5 to +25 degrees C. as being the same as for 
iron. Similarly, Christophe, in "Le Beton Arme," page 706, 
quotes Bouniceau, Meier, Bauschinger, Adie and Durand-Claye 
in stating that the coefficient may vary from .00000667 ^^ 
.00000805 P^'' degree F., and that it is essentially constant even 
with varying percentages of mixture. 

Berger and Guillerme, in "Ciment Arme," page 84, quote 
Durand-Claye as giving the coefficient of expansion but little 
different from .0000075 P^^ degree F. 

In the early part of 1902 tests were made by Messrs. J. G, Rae 
and R. E. Dougherty, graduating students in Civil Engineering 
at Columbia University, on one bar of 1:3:5 gravel Portland ce- 
ment concrete and one i :2 mortar bar, the bars being four inches 
by four inches in cross-section and about three feet long, with 
an age of about five and one-half years. 

The results found are as follows : 



Mixture 


Coefficient of Expansion per Degree Fahrenheit 


1:3:5 
1:2 


.00000655 
.00000561 



Art. 14.] THE ACTION OF SEA WATER ON CEMENTS. 45 

The tests were made under the direction of Professor W. Hal- 
lock of the Department of Physics of Columbia University, and 
the results are believed to be accurate. 

It appears therefore that the thermal linear expansion of ce- 
ment mixtures does not differ materially from that of iron. 



Art. 14. — The Action of Sea Water on Cements. 

The prevention of the disintegration of cement mixtures by 
sea water or by water containing solutions of salts has long been 
a question of dispute among chemists, although the reasons for 
its occurrence are fairly established. Sea water contains small 
percentages of magnesium-sulphate and magnesium-chloride, in 
addition to the ordinary salt, sodium chloride. The magnesium- 
sulphate and magnesium-chloride react either on the hardened 
cement or on the hydrated lime which is present in the cement 
and form calcium-sulphate and calcium-chloride. The calcium- 
sulphate crystallizes and expands, and therefore disintegrates the 
mass, but the calcium-chloride is soluble and simply deposits 
inert magnesia. 

Dr. Michaelis believes that this chemical action can be an- 
nulled by adding to the cement some pozzalana, which, in com- 
bination with lime, has of itself the property of hardening under 
water. The lime which is needed must separate from the cement, 
since pozzalana does not harden by itself. Candlot and others 
think, however, that the difficulty is more easily solved by mak- 
ing the cement mixture impermeable to the water, and that, in 
order to avoid disintegration, it is simply necessary to prevent 
the sea water from attacking the interior of the mass. They be- 
lieve, then, that if the addition of pozzalana is of value, it is only 
so because it provides a denser mixture. 

Le Chatelier has formulated a new opinion on this question 
and attributes the disintegration, in large manner, to the pres- 
ence of alumina. In that case the sulphates in the w^ater attack 
the aluminate of lime and form sulpho-aluminate of. lime, which 
swells and expands. Under those conditions Le Chatelier con- 
siders it advantageous to have as little alumina as possible in the 



46 GENERAL PHYSICAL PROPERTIES, [Ch. III. 

cement, or to replace it as far as possible by iron oxides. No ex- 
tended tests have as yet been applied to this theory. 

A complete discussion concerning the first two opinions may 
be found in Vol. XXXVII. of the Transactions of the American 
Society of Civil Engineers, including also a final statement of 
the Association of German Portland Cement Manufacturers upon 
the proposition of Dr. Michaelis. In this particular instance it 
is declared that cement mixtures for use in sea water are not im- 
proved by the addition of pozzalana or trass. 

R. Feret has presented a paper, in Vol. IV., 1901, of the "An- 
nales des Fonts et Chaussees," concerning the efifect of the addi- 
tion of pozzalana to Portland cements which are to be used in 
sea water. In the paper are recorded tests made upon several 
specially manufactured cements, marked G, R, T and A, which 
were afterward used in actual construction work in harbors. The 
G cements consisted of equal weights of good Portland cement 
and of lightly burned gaize'^; the R cements consisted of equal 
weights of good Portland cement and Roman pozzalana; the T 
cements, of equal weights of good Portland cement and trass, 
and the A cements were m.anufactured from pastes containing 
about 23 per cent, of clay. The results obtained from these ce- 
ments were compared to Portland cements of various brands, 
manufactured from a paste containing about 21 per cent, of clay. 
Tests were made in the waters of the harbors of Boulogne, Calais, 
Havre, La Rochelle and Bordeaux. The longest tests extended 
over a period of three and one-half years; and although the re- 
sults obtained were not in all respects harmonious, it was found 
that the mortars made of the specially prepared cements were, in 
general, stronger and showed less signs of disintegration than 
the mortars made from the ordinary Portland cements. This 
was found to hold true, however, only when the mixtures were 
deposited under water. When the mixtures were allowed to 
harden in air it was found that the specially prepared cements 
possessed little strength, even after an interval of two years. The 
ordinary cements naturally attained their usual strength. Feret 



*Gaize— A light, porous stone of variable degree of hardness, resulting from the silification 
of certain clays. 



Art. 14.] THE ACTION OF SEA WATER ON CEMENTS. 



47 



finally concludes that the most useful mixture, as well as the 
most economic, is made by grinding together two parts, by 
weight, of Portland cement to one of gaize. Such a cement has 
been specially made, and is now being subjected to tests in the 
harbors of Bordeaux and Boulogne. 

There are two ways of depositing concrete in sea water — 
either as blocks, which have already set in air, or by depositing 
the plastic concrete, by means of buckets, under the water. 
These two methods admit still of two other variations. Concrete 
may be mixed either with fresh water or with salt or brackish 
water. There is at present a lack of reliable information as to 
the final resistance of concrete prepared in any of these ways, 
although the question is being studied with great care by the So- 
ciety of German Portland Cement Manufacturers, who estab- 

TABLE I. 



Mixture 



Ratio in Percentages of Tensile Strength of Sea 
Water vs. Fresh Water Hardening 



Age in Weeks 



1 



26 



52 



104 



I Cement, I Sand 

I Cement, 2 Sand 

I Cement, 4 Sand 

I Cement, 4 Sand, % Hydrat Lime 
I Cement, I Sand, ]4. Hydrat Lime 



92.0 
89.3 
92.6 
99.4 
91.5 



93.7 
92.2 
92.7 
88.8 
67.7 



93.3 
90.0 
77.5 
87.1 
76.3 



89.6 
90.5 
78.6 
74.3 
77.6 



92.6 
88.2 
80.5 
87.7 
74.0 



lished, in 1894, with the aid of the Prussian government, an ex- 
periment station on the island of Sylt, in the North Sea. It is 
there also that it is proposed to determine finally the soundness 
of the theory advanced by Dr. Michaelis concerning the admix- 
ture of pozzalana in concrete which is to remain in sea water. 

Strength in Sea Water — The strength of cement mixtures does 
not increase as rapidly in salt water as in fresh. Experiments 
set forth by Dyckerhofif in the Proceedings of the Association of 
German Portland Cement Manufacturers, 1896, are shown in 
Table L, in which are given the ratios in percentages of tensile 
strengths of mortars hardening in salt and fresh water. The 
table shows some irregularities in regard to the mixtures includ- 
ing lime, the older mixtures of which, although furnishing high 



48 



GENERAL PHYSICAL PROPERTIES. 



[Ch. III. 



resistance at the time of setting, also showed marked signs of 
disintegration. 

Table II. furnishes very similar results, and is taken from 
Biising and Schumann's "Portland Cements," page 128, from 
experiments made by Sympher on the crushing resistance of 
mortars when deposited in weak sea water. The relations be- 
tween results of the fresh and sea water specimens' is very satis- 
factory, although in the last case shown the specimens were at- 
tacked and partially destroyed in the sea water. 

Table III. is taken from the Report of the Boston Transit 
Commission for the year endmg June 30, 1902, and shows the 
efifect of keeping briquettes in compressed air, in fresh water and 





TABLE 


n. 






Mixture 


Hardening in 


Ultimate Crushing Resistance in Lbs. per Sq. In. 
at tiie Age of 


4 
Weelis 


52 
Weelis 


104 

Weeks 


Remarks 


I Cement, I Sand. . •< 

I Cement, 2 Sand. . < 

I Cement, 3 Sand. . f 
% Hydrat Lime. • • • ( 


Fresh Water. 
Sea Water. . . 
Fresh Water. 
Sea Water. . . 
Fresh Water. 
Sea Water. . . 
Fresh Water. 
Sea Water. . . 


4230 
3440 
3640 
3530 
2840 
2340 
2210 
2II0 


6330 
4340 
5000 
4320 
3560 
3400 
2640 
2340 


6880 
5420 
5300 
4590 
4190 
3820 
2880 
2340 




I Cement, 4 Sand. . f 
l4 Hydrat Lime. • •• \ 


Edges broken off; disin- 
tegration in sea water 



in sea water. The briquettes were of the usual type used in 
tensile testing, the mixture used being i part of cement, 2^ parts 
of fine crushed stone^ ranging in size from an impalpable powder 
to J inch in diameter, and 4 parts of coarse crushed stone, J to ^ 
inch in size. All the briquettes were kept in air at 60 to 80 de- 
grees Fahr. for the first twenty-four hours after making, and 
then in compressed air at a pressure of 18 to 25 pounds per 
square inch for thirteen days; they were then divided into three 
lots and placed as shown in the table. Each figure is a mean of 
three briquettes. The results shown belong to Vulcanite cement 
only, but other brands acted similarly. 

It will be seen that the briquettes kept in compressed air were 
always the strongest, and that up to the age of four months there 
was no practical difference between those kept in fresh water and 



Art. 14-] 



THE ACTION OF SEA WATER ON CEMENTS. 



49 



in sea water ; but at nine months the sea water briquettes did de- 
preciate considerably in strength. 

R. Feret has recorded in Vol. CVII. of the Proceedings of the 
Institution of Civil Engineers, page 163, some very interesting 

TABLE III. 



Place of Keeping the Briquettes 


Average Tensile Strength in Lbs, per 
Square Inch at 




1 Month 


4 Months 


9 Months 


Compressed Air (18-25 Pounds Pressure). 

Fresh Water (Changed Each Day) 

Sea Water (Under the Harbor) 


440 
460 
420 


617 
501 

533 


866 
662 
543 



experiments on the hardening of cement mortars in fresh and sea 
water. Table IV. is an abstract of these tests. Each result 
shown is a mean of six tensile briquettes of .775 square inch 
cross-section and of two compressive cubes whose area of cross- 
section was 7f square inches. 

TABLE IV. 

Ultimate Resistance in Lbs. per Square Inch 





Neat 
Cement 


Mortars Composed of 
1 Cement, 3 Standard 
Quartz Sand, by Weight 


Mortars Composed of 1 Cement, 3 Fine Gravel by Weight, 
Mixed with Trowel to Plastic Consistency 


Age 


Mixed With and 

Immersed in 

Sea Water 


Mixed With and 

Immersed in 

Sea Water 


Mixed With and 
Immersed in 
Fresh Water 


Mixed With Fresh 

Water and Kept 

in Air 




Ten- 1 Ten- 
sion 1 sion 


Ten- 
sion 


Com- 
pression 


Ten- 
sion 


Com- 
pression 


Ten- 
sion 


Com- 
pression 


4 Weeks. .. 
12 Weeks.. 
I Year 


422 


149 


95 

115 
179 


327 


71 

88 

146 


469 


70 

77 

173 


426 


736 


275 


540 


731 


838 



It will be seen that the tension and compression tests do not 
furnish uniform results; the tension specimens hardening in sea 
water are stronger than those hardening in fresh water. This is 
not true of the compressive specimens, whose crushing resist- 
ance, moreover, is exceptionally low. The cement used in these 



50 



GENERAL PHYSICAL PROPERTIES. 



[Ch. III. 



tests had the following fineness : 50 per cent, passed a sieve hav- 
ing 32,300 meshes per square inch; 31 per cent, passed a sieve of 
5,800 meshes per square inch, but was retained by previous 
sieves, and the remaining cement was retained on the 5,800 mesh 
screen. 

It may then be concluded that, unless mixtures fail by disin- 
tegration, their strength under sea water approximates that at- 
tained under normal conditions, but is never greater. And, 
finally, disintegration may be avoided, either by making the 
mixture impermeable or by adding some substance such as poz- 
zalana. 

Gauging with Salt Water — The action of ordinary salt solu- 
tions on the strength of cement mixtures still remains to be con- 
sidered. 

Figure i is taken from tests reported by A. Noble in Vol. 
XVI., 1887, of the Transactions of the American Society of 
Civil Engineers. The figure shows the effect on the tensile 
strength of one cement to one sand mortar briquettes when 
m.ixed with water containing various percentages of salt. It 
will be seen that there is but very little loss in strength when the 

water contains small per- 
centages of salt, and not 
much more loss even 
when the percentages rise 
to 16. 

E. C. Clarke records 
very similar experiments 
in Vol. XIV. of the same 
Transactions; in this case 
briquettes were gauged 
with fresh water and with 
salt water, and were also 
immersed in both fresh and salt water; the results show no great 
variations in strength. Clarke states that the time of setting is 
somewhat retarded; in this he is corroborated by Heath, page 83, 
of his Manual of Limes, Cements and Mortars. 
C. S. Gowen records in a paper read before the American So- 



% 100 



S 300 



*f 200 



100 




Age of Specimens, 
FIG. 1.— NOBLE'S TESTS. 



Art 15.] 



POROSITY AND PERMEABILITY, 



51 



ciety of Testing Materials, July 3, 1903, results of tensile tests 
made on the usual standard briquettes as to the effect of salt 
water in gauging mortar under normal laboratory temperature 
conditions; the briquettes were composed of one part of cement 
and two and three parts of quartz sand. It will be seen (Table 
V.) that at the end of a year there is no appreciable difference in 
strength between the specimens which were gauged with fresh 
water or salt water. 

The salt water was about a 10 per cent, solution; each result 
shown is an average of ten breakings. It may therefore be defi- 
nitely stated that gauging cement mixtures with salt water does 
not affect the ultimate strength injuriously. 

TABLE V. 





1:2 Briquettes 


1:3 Briquettes 


Age 


Tensile Strength in Lbs. per Square Inch, Gauged with 




Fresh Water 


Salt Water 


Fresh Water 


Salt Water 


7 Days 


236 
289 
414 
549 
554 
572 


126 
231 

294 
424 
452 
576 


112 
183 
268 
335 
351 
458 


68 


I Month 

3 Months 

6 Months 

9 Months 

12 Months 


131 
215 
266 
301 
413 



Art. 15. — Porosity and Permeability. 

Porosity and permeability are terms often confused in meaning 
when applied to cement mixtures; but they apply to entirely dif- 
ferent properties. Porosity is a measure of the voids and gives 
no indication of the connection of these voids with one another. 
Permeability, on the other hand, implies paths from one void to 
another. The question of porosity is not of the greatest impor- 
tance, except as giving indication of the denseness of a mixture 
and perhaps, indirectly, an indication of its ultimate strength. 

Due to the fineness of grinding and to the uniformity of grain, 
it is to be expected that neat cements should be more porous 
than mixtures of sand and cement. This is perhaps the more 
evident when neat cement is compared to concrete, since in 
the latter possibly 50 per cent, of the mass consists of large 
pieces of dense stone. However, in the case of concrete, it is 
clear that paths between the voids are more likely to exist than 



52 GENERAL PHYSICAL PROPERTIES, [Ch. III. 

in the case of neat cement, and that, therefore, the concrete may 
be the more permeable. 

R. Feret, in a very valuable paper* published in Vol. IV., 1892, 
of the ''Annales des Fonts et Chaussees," discusses fully the po- 
rosity and permeability of various kinds of cement mortars, and 
shows that the actual solid contents of a mixture are cleaifly indi- 
cated by the amount of water absorbed. He states that a mix- 
ture in which the fine sands predominate is always the more 
porous; the permeability, however, varies inversely to the po- 
rosity. 

Feret's experiments were carried on with three sizes of sand 
grains; a coarse sand, which would correspond to a sand passed 
by a No. 5 sieve and retained on a No. 12 sieve; a medium sand, 
which would correspond to a sand retained between a No. 12 and 
a No. 50 sieve, and a fine sand, all of which would pass a No. 50 
sieve. 

Feret's Conclusions — It is perhaps best to quote Feret's con- 
clusions directly:! 

(a) The permeability of a mortar depends less on the total vol- 
ume of the voids than on their individual dimensions. 

(b) The continuous passage of water through mortars dimin- 
ishes the permeability very rapidly. 

(c) The filtration of sea water through mortars often results in 
their more or less rapid disintegration. 

(d) All other things being equal at the beginning of filtration, 
plastic mixtures are less permeable than dry; after some time 
this difference disappears, and it appears that, in the case of sea 
water, disintegration is not more rapid for one than for the other. 

(e) In general mortars made with the same sand are the less 
permeable, as they contain the more cement. 

(f) Mortars of the same richness, but of diflferent granulometric 
sand composition, are disintegrated by the passage of sea water 
as rapidly as in proportion to the fine grains in the sand. The ef- 



*.S?/r la Compacite des Mortiers Hydrauliques. 
^Page 14J of Ferefs paper. 



Art. 15.] 



POROSITY AND PERMEABILITY. 



53 



fects may not be the same for mortars which are simply placed in 
water. 

A very full discussion on impervious concrete is also recorded 
in the Transactions of the American Society of Civil Engineers, 
December, 1903, and the work of 
various experimenters is cited. 
The general conclusion, there 
summarized by R. W. Lesley, is 
as follows: That neat cement 
mortars show the least permea- 
bility; that mortars with fine 
sand are less permeable than 
those mortars with coarse sand, 
and that the lessening of the per- 
meability is due to the closing of 
the pores by hme, which is car- 
ried in suspension, in the process 
of filtration, through the mass, 
and which ultimately forms a 
coating on the surface of the ma- 
sonrv. 




10 15 

Age in Days 

FIG. 1. 



In almost all cement mixtures, 
even if permeability does exist in 
the beginning, it decreases very 
fast as the mixture ages, provided disintegration does not take 
place. This is very clearly shown by experiments reported in 
Vol. CVIL, page 95, of the Proceedings of the Institution of 
Civil Engineers. Figure i is taken from that report and shows 
the filtration of sea water under a head of twenty-four feet, 
through one cubic foot of Portland cement concrete of the pro- 
portions indicated, three months old. It is seen how rapidly the 
amount of water which passes through the mass decreases with 
the time, even for widely varying proportioned mixtures. 

Figures 2 and 3 are taken from Feret's paper, already noted. 
Figure 2 shows the initial permeability of two series of mortars, 
mixed with different proportions of sand and gauged with dif- 
ferent percentages of water. The size of the specimens and the 



54 



GENERAL PHYSICAL PROPERTIES. 



[Ch. III. 



surface through which the water passed are not given; the speci- 
mens set in air two weeks before being tested. The small initial 
permeability of the richer mixtures is immediately noted. 



7060 



s 

» 3530 



\ 








cu.ft.l 




Initial Permeability 


per hr.\ 


\ c 


of 2 Series of Mortars 
of diflEerent Consistencies 


cu.f«. 


\l 




per hr. 


K%. 










e/. 



( 7.3 Sand i.9 Sand 3.6 Sand 

\ 1 Cement 1 Cemeat _ 1 Ceooent 

Parts of Sand to Cement 

FIG. 2.— FERET'S TESTS. 



Figure 3 shows the variation in the permeability of three mor- 
tars during the two first days of filtration; the experiments were 
continued for one year, and at the end of that time it was found 
that the percolation through the lean mixture had ceased, but 



21180 



11120 



7000 



3530 




Variatfon of Permeability 
of 3 Mortars during the 
first days of filtration 



» 6. 12 24 36 4& Houra 

Time Elapsed from Beginning of Filtration. 
FIG. 3.— FERET'S TESTS. 



that the other richer mixtures had been slightly attacked by sea 
water and were passing very small quantities of water. 

Feret notes that the permeability decreases the more rapidly as 
the first filtration is the more abundant, and that the amount 



Art. 16.] EFFECT OF FREEZING ON CEMENT MIXTURES. 55 

passed is independent of the nature of the Uquid (fresh or sea 
water). 

In conclusion, inspection of existing concrete work is sufficient 
to show that almost any well balanced mixture can be made im- 
pervious to the passage of liquids; the greatest care in mixing, 
due to the non-homogeneity of the ingredients, must be observed. 
Where concrete masses do pass water, the permeability will in 
general be found to be due, not to some defect in the concrete 
itself, but to open cracks which may have been caused from one 
of various reasons, such as improper joining of work laid at dif- 
ferent times, settlement of foundations or temperature changes. 

The addition of salts or soaps to cement mixtures to cause im- 
permeability has not been considered by the author; although 
many experiments have been made along such lines, the results 
are not in such form as to warrant the drawing of definite con- 
clusions, the more so when it seems possible to make cement 
mixtures impervious without such aid. 

Art. i6.— The Effect of Freezing on Cement Mixtures. 

The effect of cold temperatures on the setting and hardening 
of cements has been much discussed, but appears at present to be 
very simple. It is now the opinion that the hardening properties 
of frozen cement are not impaired, if the freezing has taken place 
before the initial setting of the cement has begun. Under those 
conditions the physical action of the changing of the water into 
globules of ice has prevented the chemical action of the crystalliz- 
ing of the cement particles ; crystallization cannot take place until 
the ice globules return to the liquid form. No damage will then 
have been done, if freezing does not again take place before the 
cement has set; but if continued thawing and freezing take place, 
allowing an intermittent action of setting, it is very likely, under 
those conditions, that the cement will be injured. Many large 
pieces of concrete work have been built in freezing weather and 
have remained for long periods of time in a frozen condition, but, 
after thawing, have shown no evil effects. It is only necessary to 
bear in mind that the physical action of freezing must so far pre- 
cede the beginning of the chemical action as to preclude the lat- 



56 GENERAL PHYSICAL PROPERTIES, [Ch. III. 

ter's taking place. The use of salt, glycerine or other substances 
in the water used for laying cements at cold temperatures seems, 
therefore, unnecessary, more particularly as there is always the 
possibility that these admixtures may prove injurious. 

The percentage of injury done by the addition of salt sub- 
stances may not be very great, and may often be nil, but it is 
probable that the use of these adulterants will cease. 

Laboratory experiments made to determine the change in 
strength of mixtures gauged with salt water must be treated with 
some caution, since in the laboratory the experiments are made 
under normal temperature conditions, whereas in practice salt is 
added to cement mixtures only during freezing weather; the 
hardening of a cement under the latter condition may be very 
different. 

It has already been shown in a preceding article that, in the 
case of laboratory experiments, there is but little, if any, decrease 
in the strength of the mixture, even when a i6 per cent, salt solu- 
tion is used. Experiments made with salt mixtures during freez- 
ing weather have shown very similar results; but it seems un- 
necessary at the present time to record such experiments in any 
detail, since, as has already been stated, concrete mixed with 
fresh water is now laid at almost any temperature, and is found 
to sufifer no ill effects, if alternate freezing and thawing do not 
take place. For such experiments with salt mixtures the reader 
is referred to tests made by E. S. Wheeler and recorded by him 
in the Report of the Chief of Engineers, U. S. Army, for 1895, 
page 2968 and following. 

The following experiments, made at the Watertown, Mass., 
Arsenal on frozen cement mixtures, gauged with fresh water, 
are of exceeding value. 

Table L is taken from the Watertown Arsenal Report for 1901, 
and shows the crushing strength of two-inch cubes which were 
left for various intervals of time in a temperature of o degrees 
and were then exposed to a temperature of 70 degrees Fahr. 
It will be seen that the compressive strength did not vary to any 
considerable degree, no matter how long the specimen had been 
exposed to the freezing temperature, if it had been exposed 



Art. 16.] EFFECT OF FREEZING ON CEMENT MIXTURES, 



57 



the same number of days at the 70 degree temperature. It is 
clear that no setting action takes place when the water in the 
mixture is frozen. 

The results of tests on three brands of cements only is ab- 
stracted, since these are characteristic examples. 

Tables II. and III. show the ultimate compressive resistance 
of two-inch cubes composed of neat Portland and natural ce- 
ments and of 1:1 mortars subjected to low temperatures at the 
times of making. These experiments are also recorded in the 
Report of the Watertown x\rsenal for 1901. 

TABLE I. 



Brand 



Length of Time at 
0° F. 



Months 



Days 



Subsequent Length 
of Time at 70° F. 



Days 



Compressive 

Strength in 

Lbs. per Sq. In. 



Star I : I Mortar ^ 

Portland Cement 



Josson 1:1 Mortar. . . < 
Portland Cement 



Hoffman 1:1 Mortar.^ 
Natural Cement 



3 
14 
21 
31 



7 
14 
21 
29 

6 
13 
20 
28 



7 
7 

7 

7 

7 

7 

7 

7 

7 

7 

7 

14 

14 

14 

14 

14 



846 

1000 

lOIO 

96 1 

981 

lOIO 

1470 

1230 

1240 

1430 

1520 

340 

327 

624 

361 

379 



In Table II. there were three general groups of specimens; 
one was allowed to set in the open air of the testing laboratory 
at the ordinary atmospheric temperature, given in the report as 
70 degrees Fahr. The specimens belonging to the other two 
groups were placed in a cold storage warehouse, where they re- 
mained dififerent intervals of time. One group was placed in a 
room whose temperature was maintained at about 39 degrees, 
and the other group in a room whose temperature was in the 
vicinity of o degrees. Specimens intended for this last room 
were mixed on cold days, with the thermometer in the neighbor- 
hood of 15 to 20 degrees Fahr., and it was intended to freeze the 



58 



GENERAL PHYSICAL PROPERTIES, 



[Ch. III. 



material as soon as practicable after mixing and use mixtures as 
wet as ordinarily employed in construction. The table shows 
clearly the lengths of time the various specimens were left under 
these varying temperature conditions and the length of time at 
which the frozen specimens were allowed to thaw under normal 
conditions. Careful examination will show that the frozen speci- 

TABLE II. 



Brand 



Star Portland . . 
Alsen Portland 



Star Portland 

Star 1:1 Mortar 

Storm King Portland 



Star 1:1 Mortar. 

Alscn Portland 

Josson Portland - . . . 
Bonneville Natural 
Hoffman Natural • . . 
Norton Natural. ... 



Star. 



Storm King. 
Alsen 



Josson 

Austin 

Bonneville 
Norton. ... 



Compressive Strength in Lbs. per Square Inch 



Specimens Set in Air 

at 0° F., and Then 

Placed in Air 

at 70° F. 



3 Mos. and 30 Days 

3620 

2320 
1 Mo. and 30 Days 

3460 

1400 

1680 
3 Mos. and 14 Days 

I3I0 
2450 

648 
1020 

579 

832 



Specimens Only in 
Air at 70° F. 



30 Days 

4570 

3900 

30 Days 

4570 

I960 

2520 

14 Days 

1970 

3780 

1 160 

800 

808 

744 

3 Mos. and 14 Days 

4410 

4 Months 

2380 

3510 

3 Months 

3II0 
3 Mos. and 15 Days 
580 

3 Months 
1720 

4 Months 

950 



Specimens in Air at 

39° F.,and Then 

Placed in Air 

at 70° F. 



3 Mos. and 14 Days 

4280 
3 Mos. and 1 Month 

2700 

6400 
3 Mos. and 8 Days 

4970 
3 Mos. and 15 Days 

1480 
3 Mos. and 13 Days 

2060 
3 Mos. and 14 Days 

1440 



mens exhibited practically no deterioration in strength, if the 
time allowed them under normal temperature conditions was 
equal to that of the specimens of the same mixture to which 
they could be compared. 

. The specimens noted in Table III. were treated a little differ- 
ently; the frozen specimens were kept frozen for various inter- 



Art. 16] EFFECT OF FREEZING ON CEMENT MIXTURES, 



59 



vals of time up to one year and then allowed to set for one day 
only under normal temperature conditions. It will be seen that 
the strength of the frozen material increased to some extent, 
showing some faint chemical action; but in no case did a frozen 
specimen one year old attain, even approximately, the strength 
of a normal specimen one month old. 

C. S. Gowen presented a paper before the American Society 
of Testing Materials, July 3, 1903, in which are also recorded 
some tests on Portland cement mortar exposed to various cold 
temperatures. The tests were made on the standard form of 

TABLE III. 





Compressive Strength in Lbs. per Square Incii 


Brand 


Specimens Set in Air at Temperature 

0° F. (One Day in Air at 70° F. 

Before Testing) 


Specimens Set in Air 
at 70° F. 




1 Month 


3 Months 


1 Year 


1 Month 


3 Months 


Star Portland 


1350 

383 
749 
986 
347 
238 
411 
206 
341 
225 


1720 
497 
703 

I2I0 
624 
241 
478 
276 
347 
274 


2724 

864 

1370 

1580 

802 

333 

428 
680 
358 


4350 


4400 


'^tar I'T Mortar 


Storm King Portland 

Alscn Portland 


2520 
3900 
3970 
724 
1 140 
1 140 
1000 
1560 


2430 

4040 

3II0 

661 


Josson Portland 


Austin Natural 


Bonneville Natural 

Hoffman Natural 


1720 
1070 


Norton Natural 


1090 


Obelisk Natural 


1240 






Average 


534 


637 


I0I5 


2256 


2085 





tensile briquettes, composed of one part Giant Portland cement 
and two parts of crushed quartz sand. Table IV. shows the re- 
sults obtained under normal temperature conditions; Table V., 
results obtained under freezing temperature. In the latter table 
each figure is an average of eight tests. It should be noted that 
the results recorded for the six months freezing temperature are 
subject to an error, due to the fact that the briquettes were con- 
tinually in air up to that time and were probably dried out. The 
briquettes of nine and twelve months, made under the same con- 
ditions, were placed in water at the end of six months, and 
showed uniform increase in strength over the strength of one 
and three months. 



60 



GENERAL PHYSICAL PROPERTIES, 



[Ch. III. 



TABLE IV. 



Tensile Strength of 1:2 Mortar Briquettes 



Age 


Number of Specimens 
Broken 


Average Tensile Strength 
in Lbs. per Sq. In. 


28 Days 


690 
215 
185 
155 
165 


441 


3 Months 


563 
657 
671 


6 Months 

9 Months 


12 Months 


663 







TABLE V. 



Tensile Strength of 1:2 Mortar Briquettes 



Series 



Tensile Strength in Lbs. per Square Inch at Age of 



28 Days 



3 Months 



6 M nths 



9 Months 



12 Months 



A 
B 
C 
D 

E 



370 
458 
371 
272 

255 



474 
455 
413 
360 
246 



366 
347 
314 
287 
300 



553 
381 
452 
567 
437 



553 
586 
510 
602 
512 



Series A. Placed in cold air, 24-32 deg. F., immediately after 
mixing; fresh water used. 

Series B. Placed in cold air, 24-10 deg. F., immediately after 
mixing; fresh water used. 

Series C. Placed in cold air, 24-32 deg. F., after taking heavy 
Gillmore needle ; fresh water used. 

Series D. Placed in cold air, 20-10 deg. F., immediately after 
mixing; brine* used. 

Series E. Placed in cold air, 20-10 deg. F., immediately after 
mixing; fresh water used. 

J. S. Costigan records in the Transactions of the Canadian 
Society of Civil Engineers, 1903, some interesting tests on the 
effects of freezing neat cements, in which various briquettes were 
moulded under a pressure of twenty pounds per square inch. 
When these briquettes were twenty-four hours old they were all 
placed in water and allowed to remain there tmtil they were 
seven days old, with the exception of some twenty-four hours 
during this period, when they were exposed to the action of 



* About 10^0 by weighty solution. 



Art. 17.] 



ADHESION OF IRON IN CONCRETE, 



frost for twenty-four or forty-eight hours. The results show al- 
most a uniform ultimate resistance, no matter at what period 
after making the specimens they were subjected to the freezing 
conditions. 

Reviewing these recorded experiments, it may be seen that no 
fear need be apprehended if specimens are frozen once only and 
then thawed out. The ultimate strength attained under those 
conditions is not appreciably lower than that attained under nor- 
mal conditions. 

Art. 17. — Adhesion of Iron in Concrete. 

Table I. shows the adhesion of iron rods in concrete, as found 
by E. Morsch and reported by him in "Beton und Eisen," Part 
III., 1903. It will be seen that the adhesion varies not only 
with the richness of the cement mixtures, but also with the per- 
centage of water used in gauging. 

TABLE I. 



Percentage of Water 



Adhesion in Lbs. per Square Inch 



Richness of Mixture 



1:1 



1:2 



1:3 



1:4 



1:5 



1:6 



1:7 



1:8 



10 Per Cent 
15 Per Cent 
20 Per Cent 
25 Per Cent 



213 

398 
313 



270 
696 
398 
427 



270 
569 
356 
328 



370 
540 
356 
342 



427 
299 
171 
114 



384 
270 
171 
170 



237 
213 
156 
128 



171 

142 
100 
100 



The table exhibits no positive fact, although, in general, the 
richer mixture furnishes the greater adhesion. Neither too little 
nor too much water is to be used in the mixing, since some in- 
termediate percentage furnishes the greatest adhesion. 

Professor Charles Spofiford made a series of tests upon the hold- 
ing power of different types of rods, which are reported in the 
same number of the publication. The concrete used was a 
Portland cement concrete of 1 13 :6, the stone used being a mix- 
ture of two parts of one-inch trap and one part of one-half-inch 
trap. The concrete was wet sufficiently so that when tamped 
into the moulds water flushed tO' the surface. The rods were all 
thoroughly cleaned by a sand blast before the concrete speci- 
mens were made. Several types of rods were used — the Ran- 



62 



GENERAL PHYSICAL PROPERTIES. 



[Ch. III. 



some rod, which is a square rod, but twisted through an angle of 
20 degrees; the Thacher rod and the Johnson rod (the two latter 



TABLE II. 



Type of Rod 



Ransomc. 



Thacher 



Johnson. 



Plain. 



Cross Sec- 
tion of Rod 
in Inches 



VzyiVz 



lYs X lYs 
Y2y-Y2 

44 

IX xl^ 
Y round 

4 4 
44 

lYi^Yz 

4 4 

iY2;^Ys 
2XxX 



Mean Area of 
Cross Sec- 
tion of Rodin 
Sq. Inches 



0.25 



0.56 
1.27 
0.18 
0.39 
1.03 
0.19 
0.37 
1. 17 
0.44 
0.56 



Cross Sec- 
tion of Con- 
crete Bloclc 
in Inches 



6x6 



8x8 



10 X 10 
6x6 
8x8 

10 X 10 
6x6 

4 4 

8x8 

44 

10 X 10 

8x8 



Length 

of Rod 

Imbedded 

in Inches. 



12 

16 

26 

12 

16 

26 

20 

24 

36 

27 

37 

50 

12 

16 

26 

20 

24 

36 

27 

37 

50 

12 

16 

26 

20 

24 

36 

27 

37 

50 

24 

31 

36 

24 

31 

36 

24 

31 

36 

24 

31 

36 

24 

31 

36 



Greatest 
Adhesion 

in Lbs. 
per 

Sq. In. 



454 
228 
291 
310 
396 
260 
388 
399 
305 
245 
141 
138 
222 
282 
223 
402 
290 
250 
238 
304 
268 
508 
410 
264 
461 
347 
259 
313 
252 
242 
271 
255 
219 
274 
243 
221 
159 
201 
185 
226 
188 
164 
42 
165 
145 



Remarks 



} 



CO 

■o, 

CO-** 

3 2 



ng 

c o 

If 

s*o» 
Cflo* 

r:o- 

JO 5' 

H 
sr 



n 



o 



} ^ 



Art. 17.] ADHESION OF IRON IN CONCRETE, 63 

being well known forms of specially rolled rods), and also plain 
round, square and flat rods. All tests were made twenty-eight 
days after mixing of the concrete. 

Table 11. shows the value of the adhesion in pounds per 
square inch obtained by these different bars. Of the various 
plain forms, it will be seen that the round bars show the greatest 
adhesion and the flat bars the least. In general the adhesion de- 
creased as the depth to which the rods were imbedded was in- 
creased, but no conclusive superiority of one kind of bar as com- 
pared to another can be shown; moreover, in many cases the 
rods did not pull out at failure, but the blocks were split. The 
true adhesion w^as not found in those cases. 

Table III. shows the values of adhesion of round iron rods, de- 
termined by Professor W. K. Hatt and reported by him before 
the American Section, International Association for Testing Ma- 
terials, at its annual meeting of 1902. The table gives averages 
of three tests each, the concrete being a mixture of 1:2:4 and its 
age about thirty-two days. 

TABLE III. 



Size of Rod 


Depth of Rod in Concrete 
in Inches 


Ultimate Adhesion in Lbs. per 
Sq. In. of Rod Surface 


7-16 Inch 


6.0 
6.4 


636 

756 


5-8 Inch 





E. S. Wheeler records, on page 2940 of the Report of the 
Chief of Engineers, U. S. Army, for 1895, a considerable number 
of tests made upon the adhesion of iron bars in cement mixtures. 
In the first set of experiments, shown in Table IV., the mixture 
was composed of one part, by weight, of Portland cement to two 
parts of sand, the latter being limestone screenings passing f -inch 
slits; the age of the mortar was one month. The bars were im- 
bedded to depths varying from 8 to 10 inches; they were in the 
form of bolts, being cut from bar iron, and were without fox 
wedges. The twisted bolts were formed by twisting a piece of 
one-inch square bar iron, the length of the twisted portion being 
8 inches. The periphery of a twisted bolt was taken to be the 
circumference of a circle whose diameter was the distance be- 



64 



GENERAL PHYSICAL PROPERTIES. 



[Ch. III. 



tween opposite corners of the bolt after twisting; a core of mortar 
of this diameter was torn from the bar in pulling. It is seen that 
the increase in resistance of the twisted to the plain bar is not 
very great. 

The tests shown in Table V. dififer only in that ordinary river 
sand was used, the mixtures used being neat, i :2 and 1 14. The 
bolts were imbedded 2 to 10 inches. 

TABLE IV. 



Description of Bolt 





Number 


Average Adhe- 


Mortar 


of Bars 


sion in Lbs. 




Tested 


per Sq. Inch 


jmcnt, 2 Sand 


3 


447 




3 


556 




3 


524 




3 


543 




4 


562 




3 


434 




3 


608 




3 


5I6 




3 


561 



Plain, % In. Diameter, Round 

Plain, I In. Diameter, Round 

Plain, 1% In. Diameter, Round.... 

Plain, yi In. Square 

Plain, I In. Square 

Plain, \% In. Square 

I In. Sq., Twisted I Turn in 8 Ins.. 
I In. Sq., Twisted 2 Turns in 8 Ins. 
I In. Sq., Twisted 3 Turns in 8 Ins. 



In the Watertown Arsenal Report for 1901 are reported vari- 
ous tests made on the adhesive resistance of Jx| inch steel bars 
imbedded in Portland cement concrete prisms 6x6x18 inches 
long. The age of the prisms was about thirty days and their 
average crushing resistance about 2,278 pounds per square inch. 
It was found that the adhesion of the rods per square inch aver- 

TABLE V. 



Mortar 


No. of Bars Tested 


Average Adhesion in 
Lbs. per Sq. In. 


Neat Cement 


5 
15 
10 


313 


I Cement, 2 Sand 


2^4 


I Cement. 4 Sand 


III 







All bolts were plain, 1 inch in diameter, and round. 

aged 204 pounds per square inch of surface, with a maximum 
value of 296 pounds and a minimum of yy pounds per square 
inch. Three other prisms, whose crushing resistance was 4,210 
pounds per square inch, gave an average adhesion of 297 pounds 
per square inch. The rods were imbedded various lengths from 
2 to 12 inches. 



Art. 17.] 



ADHESION OF IRON IN CONCRETE. 



65 



Considere has made some experiments upon the adhesion of 
iron rods in concrete in a different way from other experiment- 
ers; and since his values are calculated upon an assumed condi- 
tion of internal stress, too much weight should not be placed on 
these results. His values for iron wire of .17 inch diameter, 
whose surface was perfectly clean, shining, and possibly some- 
what greasy, were foimd to vary from 70 to 170 pounds per 
square inch of surface, for concrete kept in the air. The re- 
sistance to sliding increased to 256 pounds for prisms of the 
same concrete, reinforced by larger rolled iron rods .24 inch in 
diameter, and in other experiments, in which the surface of the 
.17 inch diameter iron wires was slightly rusted, the sliding re- 
sistance varied from 330 to 500 pounds per square inch. In 
these last tests the specimens were kept under water. He found 





TABLE 


VI. 








Resistance per Sq. In. 


Resistance perSq. In. 


Diameter of Wire 
in Inches 


Condition of Wire Surface 


of Surface at Cessa- 
tion of Adherence 


of Wire Rod at Ces- 
sation of Adher- 






in Lbs. 


ence in Lbs. 


0.14 


Smooth 


502 


33500 


44 


Barbed, with Split Ends 


493 


33100 


0.12 


Smooth 


442 


35200 


" 


Barbed, with Split Ends 


423 


34000 


O.IO 


Smooth 


286 


27400 


44 


Barbed, with Split Ends 


356 


34100 



that the resistance to sliding bore some relation to the amount of 
water used; for instance, in three prisms made alike and in 
which the first had an excess of water, the second was normal 
concrete and the third was too dry, the resistances were respect- 
ively 155, 170 and 70 pounds per square inch. 

De Joly records in Vol. IH., 1898, of ''Annales des Fonts et 
Chaussees," some very interesting experiments which he made 
on the adhesion of anchor rods fastened by means of neat Port- 
land cement in holes drilled in granite blocks. Three sizes of 
round iron rods were used — .14, .12 and .10 inches in diameter. 
The depth of the holes in the granite blocks was 23.6 inches. 
The cement was allowed to harden one month in air. De Joly 
comes to this very interesting conclusion : That the ultimate ad- 



I 

66 GENERAL PHYSICAL PROPERTIES, [Ch. III. 

hesive resistance does not depend on the surface of contact be- 
tween the two materials, but on the elastic limit of the inserted 
iron rod. 

Table VL, which is characteristic of several series of experi- 
ments, shows how the adhesive resistance per square inch of 
contact surface varies at the cessation of adherence between the 
two materials from 286 to 502 pounds per square inch ; but if the 
adhesive resistance is expressed in pounds per square inch of the 
rod cross-section the values so obtained show no very great 
variation for the different sizes of rods. 

Experiments are recorded by De Joly for various qualities of 
iron rods and show very uniform results, according to this 
method of reasoning, which is correct, when the length of bar 
imbedded is so great that the ultimate resistance developed by 
the adhesion is greater than the resistance of the imbedded bar 
at its elastic limit. 

In conclusion, it seems proper to take the ultimate adhesive 
resistance of iron rods in concrete as between 250 and 400 
pounds per square inch of surface. 

Art. 18. — The Fatigue of Cement Mixtures. 

The question of the fatigue of cement mixtures has lately re- 
ceived some discussion, although the matter is probably not of 
the very greatest importance. Professor J. L. Van Ornum has 
presented in the Transactions of the American Society of Civil 
Engineers, December, 1903, a paper in which he records com- 
pressive tests made upon neat Portland cement cubes two inches 
on the side, which were crushed when four weeks old. The ulti- 
mate strength was determined in the usual way with one con- 
tinuous application of the load, and, in addition, similar blocks 
were subjected to repeated loadings of certain percentages of the 
ultimate strength, varying from 95 to 55 per cent, of the same. 
In the latter case the load was applied and removed repeatedly 
until failure occurred. Figure i shows the results obtained from 
ninety-two tested blocks. 

The same subject has also been considered by De Joly, who 
has recorded the results of his experiments in "Annales des 



Art. 18.] 



THE FATIGUE OF CEMENT MIXTURES, 



67 




Fonts et Chaussees," Vol. III., 1898. He experimented on the 
usual type of tensile briquette, whose ultimate tensile resistance 
for one application of a load 
was first found. Similar 
specimens of the same age 
were then tested under re- 
peated applications of a 
stress considerably lower 
than the ultimate, and it 
was found that the speci- 
mens broke under a vary- 
ing number of repetitions. 
This number of repetitions increased rapidly with the age of the 
specimens. 

In Table L, which is characteristic of a series, De Joly shows, for 
instance, that a specimen which broke under a tensile load of 187 
pounds at the end of two days could naturally not sustain a load 
of 200 pounds per square inch, but that at the end of three days, 
when one application of 276 pounds caused failure, it required 



1000 2000 3000 iOOO 5000 
Number of Repetitions producing failure 

FIG. 1. 







TABLE I. 




Brand of Cement 


Age of 

Specimen 

in Days 


Average Ultimate Tensile 
Resist, in Lbs. per Sq. In. 
One Application of Load 


No. of Application of Ten- 
sile Stress of 200 Lbs. per 
Sq. In. Before Rupture 


Candlot 


2 
3 
4 
•3 
6 
17 
3 
3 
7 


187 
276 
390 
403 
303 
663 
212 
347 
420 







18 

346 

2813 

>2I720 

103600 

I 

97 

>3000 


i4 


.. 


.. 


Dcmarle 



eighteen applications of 200 pounds per square inch to cause 
rupture. The table is otherwise self-explanatory. De Joly's ex- 
periments were performed so that the time of application of each 
load was almost instantaneous, being approximately i-io of a 
second. 

In order to determine the effect of a slower application of a 
load, De Joly made a series of experiments, the results of which 



68 



GENERAL PHYSICAL PROPERTIES. 



[Ch. III. 



are shown in Table 11. In this case the rapidity of the applica- 
tions varied from 92 to 26 per minute, and it will be seen how 

TABLE II. 



Age of 


Ultimate Tensile 

Resistance in Lbs. 

per Sq. In., with 

One Application 

of Load 


Number of Applications of a Load, Intensity of 200 Lbs. 
per Square Inch Before Rupture 


Specimens 
in Days 


Rate of Application 




92 per Minute 


52 per Minute 


26 per Minute 


4 
5 

6 
7 


271 
328 

361 

364 



7 

36 

16 


2 
34 

174 

173 


75 

398 

More than 

2300 

None less than 

3000 



very rapidly the number of applications increased as the time be- 
tween applications increased. Table I. seems to indicate that 
there might be a limit of fatigue to a material, so that a load, if 







TABLE 


III. 










Age of 
Briquette 


Number of 

Applications 

of Tensile 

Load of 200 

Lbs. per 

Sq. In. 


Ult. Resistance in Lbs. per Sq. In. 




Brand of 
Cement 


After One Appli- 
cation of Load 


After Treatment 
as in Column 3 


Remarks 




Ten- 
sion 


Com- 
pression 


Ten- 
sion 


Com- 
pression 




Dcmaric . 
Dcmarle . 
Dcmaric . 
Dcmaric . 
Dcmarle • 
Dcmaric • 
Candlot. . 
Candlot. . 
Sollicr. . . 
Sollicr. . . 
Dcmaric . 


12 days 

14 " 
7 " 

15 " 
20 " 

1/4 years 

7 days 

II " 

4/4 months 

5 

1/4 years 


5000 
// 

6500 
20000 

40000 


558 
525 
421 
560 
573 
857 
552 
576 
681 
708 
848 


4800 

5380 

3600 

6400 

6900 

14800 

5350 

7300 

9470 

10200 

14400 


507 

521 

400 

545 
523 
834 
490 
545 
618 
666 
826 


4900 

5070 

3620 

6170 

6950 

13450 

5420 

7100 

9860 

10300 

I4I00 


(No rest after 
repeated load- 
ing. 

Tested 24 hrs 
after repeated 

(loading. 

( 1 i4 hrs' rest 

< after repeated 
loading. 

( No rest after 
repeated load- 
ing. 

(48 hrs' rest 
after repeated 

(loading. 

(48 hrs' rest 
after repeated 

( loading. 

(No rest after 

< repeated load- 
ing. 

(Av'ge 12 hrs' 
Jrest after re- 
( peated load'g 
(No rest after 
{ repeated load- 
(ing. 

(48 hrs' rest 
i after repeated 

(loading 

(48 hrs' rest 
after repeated 

(loading. 



Art. 18.] THE FATIGUE OF CEMENT MIXTURES, 69 

applied sufficiently, although below the rupture point, might 
finally cause failure. Table 11. shows, however, that, given suffi- 
cient time between applications, the material may not sustain 
any injury. 

Table III. is also abstracted from De Joly's paper; it shows 
the ultimate tensile and crushing resistance of a cement of vari- 
ous ages, first, when subjected to only one application of the 
final load, and also, of similar specimens, after the elapse of 
various periods of time after having been subjected to repeated 
applications of a tensile stress of 200 pounds per square inch. 
Each result shown is an average of three tests, the specimens 
used being the French type of tensile briquette. 

It will be seen in this case that, although the final tensile re- 
sistance is slightly lowered, no appreciable change occurs in the 
compression pieces. 

It will require many experiments of a character similar to 
these quoted to determine definitely whether there is in concrete, 
as there is in steel, a critical point above which the material 
should never be stressed if it is never to fail at loads below the 
usual ultimate resistance. 



CHAPTER IV. 
ELASTIC PROPERTIES IN GENERAL. 

Art. 19. — Treatment of Stress-Strain Curve. 

The deformation that appears in a material which is subjected 
to any form of stress determines, in connection with the stress, 
its elastic properties. A diagram which shows the stress-strain 
relations throughout the entire range of stress is, therefore, of 
great assistance in showing clearly the elastic properties of any 
material. 

In direct tension and compression tests this diagram consists 
of a curve which shows the relative elongation or shortening of 
the specimen for each intensity of stress; in flexure tests the 
curve illustrates the ratio between deflections and the loads ap- 
plied, and in torsion tests the ratio between the twist and the ap- 
plied moment. In this treatise, however, torsion stresses will not 
be considered. 

The stress-strain curve for tension and compression speci- 
mens needs no explanation, but it will be well to consider its 
algebraic equivalent. The general designation of this relation is 
the coefficient or modulus of elasticity. It is usually denoted by 
E and expresses the ratio for any stress between the unit stress p 
and the unit strain /; that is, 

-=f • • • • (^) 

This ratio E does not possess a constant value for any ma- 
terial between a point of no stress and the ultimate; that is, the 
ratio is never represented by a straight line between the origin of 
co-ordinates and the point representing the breaking load. The 
curve is, indeed, very complex for the majority of materials used 
in construction; but it is a straight line from the zero stress to a 



Art. 19.] 



TREATMENT OF STRESS-STRAIN CURVE, 



71 



point called the elastic limit, the latter point being, in fact, that 
point where E changes in value. 

In the case of some materials it has been found that every 
stress, however small, causes a permanent strain or set to remain 
in the specimen after the removal of the stress. This involves 
slightly the proper method of calculating E. It may be deter- 
mined by dividing the unit stress either by the total unit strain 
in the specimen or by the elastic unit strain, which is the total 
unit strain less the unit set. In the opinion of the author, the 
proper method to employ is the second, which determines what 
will be called hereafter the "elastic" coefficient of elasticity. 



2000 
1900 
1800 
1700 
1600 
.S 1500 

S'uoo 

S.1300 

J 1200 

cUOO 

plOOQ 

I 900 

> 800 

S 700 

g 600 

6 500 

100 

300 

200 

100 



>f 






































// 






1 














y 


'/ 






/ 














/> 








/ 












/ 


X 








f™ 












//' 










1 










A 


y 










"^ 










y 












c 

0) 








•A 


//f 












-1 










y' 


















&W^ 




Cylindi-ical Spacimen 
of Neat Cement 
Height 39.4 Inches j 
Diameter 9i.8 Inches )' 
89 Days Old 
Beported by Bach. 
Zeitsch.Ver.Deutsh.Ing. 
Nov. 28, 1896 




is 






.MP 






? 






<^Y 


J 






3 

o 




J 


^/ 












y 










'\ 




vf 










1 






















^ 






















! / 


V 




















./ 






















/ 























3 15 6 7 8 

Decrease in Length per Inch of Specimen.in..0001 Ina. 

FIG. 1. 



.10 



This method is illustrated by Figure i, which is taken from a 
test on a round cylindrical specimen of neat cement 39.4 inches 
high, 9.8 inches in diameter and 89 days old, reported by Pro- 
fessor C. Bach in the "Zeitschrift des Vereines Deutscher In- 
genieure," February 28, 1896. Three curves are shown, the 
curve marked elastic strain being obtained by subtracting from 
the curve of total strain the curve of sets. The curve of sets, it 



72 ELASTIC PROPERTIES IN GENERAL. [Ch. IV. 

should be noted, is obtained by determining for the load indi- 
cated in the figure, the strain remaining in the material after the 
load is entirely removed. This curve of elastic strain may be ex- 
pressed by an algebraic equation, which Professor Bach thinks 
may take the following form : 

^=7 <^> 

in which £ represents the coefficient of elasticity; /, the unit 
stress applied to the specimen; /, the corresponding elastic 
strain, and n, a numerical exponent. As already explained. In 
the case of a majority of materials used in engineering work, 
this curve of elastic strain is a straight line up to the elastic limit. 
For that portion of the curve the coefficient n becomes equal to 
I and the coefficient of elasticity is a constant quantity. 

To find the tangent of the inclination — of this stress-strain 

a/ 

curve at any point, it is only necessary to differentiate the equa- 
tion jS= — . There will then be obtained 

dp E 

— r= (3) 

When p equals o, and when n is greater than i, Eq. 3 shows 

that — =C]C)and the tangent becomes vertical at the origin of co- 
dl 

dp 

ordinates. If n is less than i, and for/=o, -—^=0, and the tan- 

al 

dp 
gent is horizontal at the same point. If n equals i, then — =^E 

dl 

and the coefficient is a constant quantity. 

Another method of calculating E determines what might be 
called the instantaneous value of the coefficient of elasticity, and 
is obtained by finding the elastic strain occurring between any 
two applied loads and assuming that the curve is a straight line 
between two such points. This involves no particular error if 
the points chosen are sufficiently near together. 

Again, the value of the coefficient of elasticity has been de- 



Art. 19.] TREATMENT OF STRESS-STRAIN CURVE. 73 

termined by finding the elastic strain between the initial load and 
any other load, assuming a straight line between two such points. 
If the curve is very flat, this also involves but very little error. 

Many experimenters ignore entirely the curve of sets and cal- 
culate the coeflicient of elasticity wholly from the curve of total 
strain. This does not determine the proper quantity, although 
it is the quantity which many investigators derive. 

The method of determining the instantaneous coefficient of 
elasticity is really equivalent to considering the stress-strain 
curve to be represented by an equation of the form 

p=Kl—MP 

in which / is the unit stress, / the corresponding unit strain and 
K and M constants. By taking the first differential of this equa- 
tion there is obtained 

dp 

dl 

that is, E, or the ratio of stress to strain, is equal to a constant 
quantity, less the product of a different constant, by the unit de- 
formation at the point considered. If M equals zero, the curve 
becomes a straight line and the value of the coefficient constant. 
One other point remains to be considered before discussing in 
detail the results of any experiments, and has reference to the 
number of times a single load should be applied before proceed- 
ing to the next higher load. Professor Bach, for instance, re- 
peats his loading between the initial load and the load in ques- 
tion until he obtains always the same value of the strain. This 
involves, in most cases, removing a load five times, and some- 
times still more. Other experimenters apply a load usually but 
once, and, after having obtained the corresponding strain, pro- 
ceed either to the next higher load or first determine the set for 
the load in question. It appears possible, by the frequent repe- 
tition of loads, to change the molecular structure of the material 
so that it fails to furnish the results which are desired. This ap- 
plies particularly to loads above the elastic limit for materials 
possessing such limit. As far as practice is concerned, however, 
in determining the behavior of materials in construction, Profes- 



74 ELASTIC PROPERTIES IN GENERAL, [Ch. IV. 

sor Bach's method seems to be the proper procedure, since in 
that case there is a constant repetition of the appHcation of the 
loads; in practice, however, the element of time which appears 
between the applications of loads is sufficiently great to allow the 
material time to recover completely. This is not the case in 
laboratory work, where the times of application of the loads can 
never be at very great intervals, although even there, as has 
been shown,* it requires but very little time for a cement mix- 
ture to be restored to its original condition. 

Since much use will be made of the reports of the Watertown 
Arsenal, it will be well to state at this point that the values of the 
coefficient of elasticity in the Watertown Arsenal reports were 
obtained, in all cases, by dividing the difference between the 
initial and some greater load by the difference between the total 
and permanent deformations for the loads in question. In that 
treatment the coefficient was then assumed to be a straight line 
between the initial load and the point of loading considered. 
Unless the coefficient is actually a constant quantity throughout 
the entire range of loading, every change of loading will furnish 
a different value. These coefficients cannot very well be called 
either the instantaneous or the elastic coefficients ; but since they 
probably do not differ greatly in value from either, they will in 
this treatise be directly compared to the true coefficients. 

Inspection of a stress-strain curve will determine at once the 
quantities which express in numerical figures the values of the 
usual elastic properties, viz., the coefficient of elasticity, the elas- 
tic limit and the ultimate resistance. 



*See Art. i8 on Fatigue of Cement Mixtures. 



CHAPTER V. 



TENSILE PROPERTIES. 



Art. 20. — Coefficient of Elasticity and Ultimate Resistance. 

A valuable paper on the tensile coefficient of elasticity of Port- 
land cement mixtures is recorded by De Joly in Vol. IIL, 1898, 
of the ''Annales des Ponts et Chaussees." His tensile tests were 
conducted on two sizes of bars, the first 41 inches long by 1x1.5 
inches in section, and the other 47 inches long by 4.7x6.5 inches 
in section. Both sizes of specimens had enlarged heads in the 
manner of the ordinary tensile briquette. The elongations, in all 
cases, were measured on a gauged length of 39 mches. Various 
specimens were made with different brands of Portland cements. 
Both sizes of specimens were made from neat cement, but con- 

TABLE I.— SPECIMENS OF NEAT CEMENT. 



No. of 
Specimen 


Age 

in 

Days 


Coefficient of 

Elasticity in 

Lbs. per Sq. In. 


Determined for a 

Tensile Stress of 

Lbs. per Sq. In. 


Ultimate Tensile 

Resistance in 

Lbs. per Sq. In. 


I 


28 
40 
40 
50 
50 
50 
50 
106 
106 


2,680,000 
3,160,000 
3,070,000 
3,550,000 
3,380,000 
3,190,000 
3,130,000 
4,500,000 
4,270,000 


187 
342 
448 
142 
256 
398 
455 
271 
542 




2 


} 483 


2 


3 


N 


3 


3 

3 


y 476 
\ 617 


4 


4 





Crete mortar specimens were made only in the large size. The 
small specimens were kept in fresh water until the times of test- 
ing, which varied; but the large specimens were always kept in 
damp air until broken; this was always thirty days after making. 
Table T shows the results obtained with the smaller sized bars 
and Table IL some results on the larger ones. 



76 



TENSILE PROPERTIES. 



[Ch. V. 



De Joly states that no definite point could be termed the elastic 
limit, but that it seemed to be very near the point of rupture for 
the neat cement specimens, and that it never fell below three- 
fourths of the ultimate resistance in the case of mortars or con- 
cretes. De Joly states that this does not seem to apply to com- 
pression tests on cement mortars, since some other experiments 
made in the Laboratory de I'Ecole des Fonts et Chaussees show 
that the elastic hmit is well defined for compression and its value 
is little greater than one-half the ultimate resistance. The coeffi- 
cients of elasticity as marked in these tables are the true or elas- 
tic coefificients. 

Examination of these tables shows that the coefficient of elas- 
ticity is greater for mortars and concretes than for neat mixtures, 
at least in the case of specimens one month old and kept in moist 
air. The coefficients increase with age in the case of neat ce- 

TABLE II. 



Composition of Specimens Ap- 
proximately in Parts by Weight 


Cross Section 

of Specimen 

in Sq. Ins. 


Average Value of 

Coefficient of Elasticity 

in Lbs. per Sq. In. 


Average Ultimate 
Tensile Resistance 


Cement 


Sand 


Stone 


in Lbs. per Sq. In. 


Neat 

I 
I 






31 
31 
31 


2,560,000 
3,000,000 
3,040,000 


338 
141 
135 


2.4 

1.5 




1.5 



ments, but do not change materially with the sizes of the speci- 
mens. In another table, not quoted, De Joly shows that the 
value of the coefficient does not change sensibly for different 
brands of cements ; he also states that the value of the coefBcient 
for tension for any one neat, mortar or concrete specimen is con- 
stant, and, as compared to the coefficient of elasticity for com- 
pression, is equal, or greater, but never less. 

The following series of tensile tests on reinforced concrete 
prisms is also recorded by De Joly in the same volume of the 
"Annales des Fonts et Chaussees" and is of exceeding interest. 
Figure i shows the character of the specimens with which the 
tests were made. The specimens of Type No. i, which were 
both neat, mortar and concrete mixtures, contained three bars 
of round iron .78 inch in diameter, placed as shown; all other 
types were neat cement only. Type No. II. contained five bars 



Art. 20,] COEFFICIENT OF ELASTICITY AND RESISTANCE. 



11 



of iron of the same dimensions, placed as shown. Type No. III. 
contained either one round bar .78 inch in diameter, placed at 
the centre and continuing throughout the entire length of the 
concrete, or two bars, as shown under the figure marked Type 
III. In Type No. IV. six specimens were prepared, each of 
which contained two bars, also of the same diameter, placed sym- 



± 



T7peIV 



Type IV 



Type III 



1".; 

OH 



Type II 



Type I 



rVio 



FIG. 1. 



metrically in the beam and continuing throughout the entire 
length; but in four of these specimens the rods were fastened 
solidly at the ends by means of fiat plates. De Joly states that it 
was impossible to determine any elastic limit from the stress- 
strain curves; it appeared to be near the point of rupture. This 
means that the apparent coefficient of elasticity is practically a 
constant quantity; it is calculated by dividing the unit stress on 
the bar, obtained by dividing the total load by the total cross- 
section, by the unit deformation of the bar. 

The addition of metallic reinforcement increases the value of 
the coefficient of elasticity of a cement mixture, but this increase 
is never more than 50 per cent.; at least Table III. shows this to 
be so for specimens of Type No. III. 

In none of the experiments was De Joly able to determine ex- 
actly the ultimate resistance of the reinforced specimens. Vari- 
ous reasons are given for this, and it is therefore better to omit 
these values. 



78 



TENSILE PROPERTIES, 



[Ch. V. 



The results given in Table III. are each an average of one to 
three specimens; in the case of the specimens of Type No. III., 
the spacing apart of the two bars is increased from the first to the 
fourth tests, there shown, so that in the fourth test the bars are 
very near the surface of the specimen. It will be seen, then, that 
the coefhcient of elasticity increases as these same bars vary their 
position within the specimens, from the centre to the outside. 
The great difficulty of making tensile tests on reinforced concrete 
specimens is clearly shown by the last statement, which shows 
the unequal distribution of stress through the cross section; rea- 
soning would tend to show that the exterior of specimens of the 
kind shown carries the greatest part of the stress. Reasoning 
further, it seems, then, that iron imbedded in the very centre of 
concrete specimens will influence the stress-strain diagram of the 

TABLE III. 



Specimen of Type 
No. 



Reinforced 
or 

Not 



I 

I 

Ill 

III. (with I bar). 
III. (with 2 bars) 
III. (with 2 bars) 
III. (with 2 bars) 
III. (with 2 bars) 



No 
Yes 
No 
Yes 



When 
Stress on 
Cross Sec- 
tion is Lbs. 



6160 



Coefficient of Elasticitv in Lbs. per Sq. In. 



Neat Cement 



2,550,000 
3,740,000 
2,560,000 
2,720,000 
3,540,000 
3,670,000 
3,820,000 
3,900,000 



Mortar 



3,000,000 
3,960,000 



Concrete 



3,030,000 
4,260,000 



Minimum cross section of all specimens about 30 square inches. 

combined material but little, and inspection of Table III. con- 
firms this reasoning. It appears, therefore, that but little knowl- 
edge can be gained of the elastic behavior of these two materials 
in combination by making direct tensile tests of the kind indicated. 

And these results are confirmed by experiments made by the 
author and recorded in succeeding pages. 

W. H. Henby has recorded in the Proceedings of the Asso- 
ciation of Engineering Societies for September, 1900, a very in- 
teresting set of experiments on the elastic properties and ulti- 
mate strength of stone and cinder concretes under both tensile 
and compressive stresses. These tests were made at Washing- 
ton University as thesis work. The tension specimens, made in 



Art. 20.] COEFFICIENT OF ELASTICITY AND RESISTANCE. 



79 



iron moulds, had a cross section of lo square inches, being uni- 
formly 2|x3-|- inches in cross section. They had a length of re- 
duced section of 14 inches and an over- all length of 21 inches. 
The compression specimens were made in wooden moulds; they 
had the same sectional area as the tension specimens, with a 



TABLE IV. 
TENSILE TESTS OF CEMENT, MORTAR & STONE CONCRETE. 



QQ 




Composition 
Parts ol! 








5| 


Modulus 


m 
<o — 






CM 



Age in 






Brand 
of 




Treatment 




of 
Elasticity 


tntf, 


Con- 




^ 


-^ 






Remarks 


^ 


Days 


c 


-^ 


CU 


Cement 


*© z 




§0 


Lbs. per 


|S. 


sistency 




£ 




c 









2I 




1* ^ 


Sq. In. 


5 r 






£3 


7 





in 


£ 




asu^ 




IS Q. 




35 






8 


2 


4 


L 


I'A 


Air dry 


— 


2,000,000 


130 


Dry 




16 


30 




2 


4 


" 


1% 


" 


142 


2,882,000 


198 


" 




17 


30 




2 


4 


" 


\'A 


ii 


148 


4,727,000 


227 


" 


Very dense spec. 


295 


64 




2 


4 


A 


2 


Air 


151 


7,744,000 


252 


*' 




315 


30 




2 


4 


" 


2 


" 


149 


8,360,000 


183 


" 


i Failed in 
[ shoulder. 


316 


30 




2 


4 


" 


2 


i« 


1485^ 


7,280,000 


214 


" 


22 


60 




2 


5 


" 


\% 


Air dry 


144 


1,857,000 


111 


Very dry 




25 


60 




2 


5 


" 


\Vi 


" 


146 


3,253,000 


128 


Dry 




26 


60 




2 


5 


" 


I'A 


" 


146 


3,023,000 


189 


*' 




30 


90 




2 


5 


M 


\Vi 


" 


140 


3,776,000 


142 


** 




105 


90 




2 


5 


A 


VA 


" 


144 


3,696,000 


129 


Very dry 




107 


90 




2 


5 


" 


I'A 


" 


144 


3,896,000 


93 


** 




287 


63 




2 


5 


" 


2 


Air 


146 


4,980,000 


154 


Dry 




288 


63 




2 


5 


" 


2 


" 


146 


3,744,000 


192 


** 




95 


30 




3 


6 


" 


2 


" 


150 


3,810,000 


119 


*^ 




271 


30 




4 


8 


" 


VA 


Water 


149 


6,108,000 


125 


ii 




23 


90 




3 


— 


M 


— 


Air dry 


136 


3,988,000 


199 


ii 


} Failed in 
) shoulder. 


24 


90 




3 


— 


" 


— 


" 


139 


5,202,000 


234 


ii 


117 


120 




3 


— 


" 


— 


i( 


135 


5,144,000 


144 


Very dry 




118 


120 




3 


— 


" 


— 


" 


136 


5,150,000 


154 


ii 




18 


30 




2 


4 


L 


VA 


" 


142 


2,269,000 


191 


Plastic 




35 


55 




2 


4 


" 


\A 


" 


147 


4,543,000 


149 


" 




65 


95 




2 


4 


" 


\Vi 


" 


146 


3,992,000 


190 


" 




66 


95 




2 


4 


" 


lA 


Air 


147 


4,760,000 


226 


" 




72 


8 




2 


4 


A 


1% 


" 


157 


3,720,000 


213 


" 




67 


100 




2 


4 


L 


\A 


Air dry 


147 


5,075,000 


209 


" 




18 


30 




2 


4 


A 


2 


Air 


148 


3,305,000 


192 


ii 




222 


30 




2 


4 


ti 


1% 


" 


153 


3,750,000 


223 


ii 




223 


30 




2 


4 


" 


lA 


" 


150 


3,600,000 


241 


ii 




224 


30 




2 


4 


" 


\A 


Water 


158 


3,550,000 


279 


" 




283 


65 




2 


4 


ti 


2 


Air 


144 


3,810,000 


143 


" 


Failed in head. 


284 


65 




2 


4 


" 


2 


" 


149 


3,724,000 


102 


" 




286 


65 




2 


4 


" 


2 


Water 


150 


5,440,000 


82 


" 




3 


14 




2 


5 


M 


\A 


Air dry 


139 


2,000,000 


85 


" 


Not well ram'd. 


5 


18 




2 


5 


" 


\Vi 


" 


— 


2,106,000 


120 


" 




78 


7 




2 


5 


A 


\A 


Air 


152 


3,958,000 


147 


" 




236 


30 




2 


5 


" 


lA 


" 


145 


4,532,000 


165 


" 


Failed in head. 


237 


30 




2 


5 


" 


\A 


" 


152 


4,425,000 


242 


" 




241 


30 




2 


5 


" 


\A 


Water 


155 


5,000,000 


239 


" 




91 


7 




3 


6 


" 


lA 


" 


154 


3,828,000 


115 


" 




242 


30 




3 


6 


" 


\Vi 


Air 


147 





130 


" 




243 


30 




3 


6 


" 


lA 


(4 


147 


2,427,000 


104 


" 




244 


30 




3 


6 


" 


\A 


" 


148 


2,440,000 


128 


ii 




245 


30 




3 


6 


" 


lA 


" 


144 


4,496,000 


93 


*' 




270 


30 




4 


8 


" 


\A 


" 


143 


3,553,000 


71 


** 




235 


95 




— 


— 


M 


— 


Water 


137 


6,423,000 


645 


*' 


Failed in head. 


10 


18 




2 


4 


" 


\A 


Air dry 


— 


2,286,000 


75 


Excess 




36 


90 




2 


4 


" 


\A 


*' 


147 


3,500,000 


125 


ii 




165 


120 




2 


4 


" 


\A 


** 


143 


3,473,000 


136 


" 




166 


120 




2 


4 


" 


\A 


(i 


144 


3,473,000 


89 







A indicates Atlas Brand Cement; M indicates Medusa Brand ; L indicates Lehigh Brand. 



80 



TENSILE PROPERTIES, 



[Ch. V. 



TABLE IV. — Continued. 
TENSILE TESTS OF CINDER CONCRETE. 



1 


Age in 


Composition 
Parts of 


Brand 






3I 


Modulus 
of 




Net Ult. 
Compress. 


g 


.4a 






of 


03 (3 


Treatment 


*i-° 


Elasticity 


■^ >- 


Resistance 


.0 


Days 


a 




a> 


Cement 


0) 




WjO 


Lbs. Per 


s °- 


Lbs. per 









c 

03 


c 









ll 


Sq. In. 


2i 


Sq. In. 


43 


7 




2 


4 


A 





Air 


118 


1,854,000 


46 





44 


7 




2 


4 






— 


** 


114 


1,892,000 


— 





46 


7 




2 


4 






— 


Water 


122 


1,826,000 


— 





141 


30 




2 


4 






— 


Air 


113 


2,800,000 


133 


993 


149 


30 




2 


4 






— 


Water 


121 


2,909,000 


77 


1,415 


159 


30 




2 


5 






— 


Air 


109 


2,853,000 


86 


1,039 


155 


30 




2 


5 






— 


" 


107 


2,329,000 


85 


1,054 


167 


30 


1 


2 


5 






— 


** 


102 


1,820,000 


78 


688 


171 


30 




2 


5 






— 


Water 


126 


1,900,000 


76 


1,166 


174 


30 


1 


2 


5 






— 


Air 


112 


1,900,000 


129 


1,005 


132 


60 




2 


5 






— 


Air dry 


117 


2,413,000 


97 


882 


2 


12 




2 


5 


M 


— 


" 


113 


1,428,000 


60 





195 


60 




3 


6 


A 


— 


" 


110 


1,274,000 


58 


699 


198 


60 




3 


6 






— 


" 


110 


1,892,000 


88 


949 


202 


60 




3 


6 






— 


" 


107 


2^15,000 


62 


677 


207 


60 




3 


6 






— 


" 


108 


2,922,000 


52 


— 


186 


30 




3 


6 






— 


Water 


114 


1,422,000 


41 


653 


209 


30 




3^2 


7 






— 


Air 


102 


1,034,000 


30 


409 


212 


30 




3y2 


7 






— 




104 


937,000 


31 


510 



Remarks 



A indicates Atlas Brand Cement; M indicates Medusa Brand ; L indicates Lehigh Brand. 

length of 1 1 inches. The deformations were determined for both 
kinds of stress by means of a dial extensometer having friction 
rollers and measuring by means of a vernier needle to .0001 of 
an inch. The tensile elongations were measured on a gauged 
length of 10 inches, the cornpressive deformation on a length of 
6 inches. Three brands of Portland cement were used — Atlas, 
Lehigh and Medusa. The sand used was Mississippi River sand 
and the stone was ij to 2 inch limestone macadam, taken in the 
same condition in which it came on the market. The total vol- 
ume of voids in the 2-inch macadam was 57! per cent.; in the ij- 
inch macadam, 6if . The cinders used were unscreened. All the 
measurements were volumetric. It was found that the average 
density of the stone concrete compression specimens was greater 
than the average density of the tensile specimens. 

Table IV. shows the ultimate tensile resistance and the modu- 
lus of elasticity of both stone and cinder concrete specimens ; they 
are tabulated in the order of their consistency, the first ones 
being the dry specimens, then the plastic, then the excess. From 
the figures accompanying the original report it may be presumed 
that the coefficients as calculated are not the true elastic coeffi- 



Art. 20.] COEFFICIENT OF ELASTICITY AND RESISTANCE, 



81 



cients, since no permanent deformations or sets were noted. If 
this be the case, the true coefficients would have higher values, 
and such high values have not been confirmed by other experi- 
menters. The results are directly comparable in themselves, 
however, since they were all made under uniform conditions, 
with the same apparatus and by the same experimenters; there- 
fore, general deductions may be made. 

The specimens which are marked ''Air" were covered with 
damp cloths; the others were either kept in the dry air of the 



300 
280 
260 
240 
220 
200 

■^ 180 
c 

ID 

S ICO 

a 

^ 140 

a, 
"2 120 

•J 100 

80 

60 

10 

20 

























































/ y 






































/ 


^/ 


/ 








1 




























/ 


k 


f 








i 


^ 






^ 


















f/ 


(a 


y / 


,^ 


-^ 


V 




i^ 


1 


/ 


^ 


/ 
















4 


/ 


A 


/ f 




/ 


1 






V 


^ 


/ 


f 




^ 


^ 
^ 










S/ 


/ 


/ 


/ 






/ 






r 




/ 




\^ 


^ 












w 


(f/i 


V 




fl 


J 


f 




^/ 


/ 


V 












i 


# 
W 


^ 


/ 


41/ 






ij 




7 




i 


V/ 


/ 
















/ 


/ 1 


^ / 








1 




/ 




} 


V 


















/ 


/ 


/ 




1 




/ 






/ 
















n?/ 




/ / 


f 




1 




/ 




















■^ 




v^' 


-V»*/ 






i 


1 




/ 


^ 


/ 
















/ 


/ 


(/ 


/ 








/ 




/ 




1 


















// 


/ 


/ 








/ 




/ 























.00001 



.00003 



.00005 



Proportionate Elongation 

V 



FIG. 2.— HENBY'S TESTS. 

laboratory or in water, as marked. Henby concludes that the 
greatest strength is developed in the case of the dry mixtures 
in which ramming is required to flush water to the surface. In 
that case the density and the ultimate strength increase together. 
The air dry specimens show lower results than the air speci- 
mens, and the concretes which set in water attained greater 
strength than either of the others. This does not appear to be 
the case, however, for the cinder concretes. The results show 
that the coefficient of elasticity increases slightly with the age of 



82 TENSILE PROPERTIES, [Ch. V. 

the specimen, and perhaps sUghtly with the denseness of the 
mixture. This is equivalent to saying that the coefficient in- 
creases with the ultimate resistance. 

Table IV. also gives tensile results found with cinder concretes. 
It will be seen that the ultimate tensile resistances are very low, 
averaging perhaps 75 pounds per square inch. The coefficients 
of elasticity are also lower than in the case of the stone concrete 
specimens and they decrease with the leanness of the mixtures. 

Figure 2 is taken from Mr. Henby's paper and shows the char- 
acteristic stress-strain curves for seven tension tests of 1:2:4 
stone concretes. An elastic limit might be placed at about two- 
thirds of the ultimate resistance. 

In some other tensile experiments, not here tabulated, Henby 
found that some cinder concrete specimens thirty-three days old, 
one part Atlas cement, three sand and six cinder, gave an aver- 
age value of the coefficient for dry specimens of 2,368,000, and 
for wet specimens of 898,000 lbs. per sq. in. It will be seen that 
the dry specimens are much more resistent to deformation than 
the wet. 

Henby also made the following experiments on eight cinder 
concrete specimens of the tensile form. All the specimens were 
first set in damp cloths for forty-eight hours and were then kept 
in dry air for twenty-eight days. Half of the batch were then 
put in water for three days. The average tensile resistance of 
the four dry specimens was found to be 89 pounds per square 
inch, and of the four wet specimens, 46 pounds per square inch. 
One half of the halves of the dry tensile specimens were then 
immediately tested to failure by compression; the other half were 
tested after being in water forty-eight hours. Also, half of the 
halves of the wet specimens were tested immediately and the 
other half were dried at 125 degrees Fahr. for forty-eight hours 
before being broken. The four specimens which had never been 
in water averaged 827 pounds per square inch; the eight wet 
specimens, 734 pounds per square inch, and the four dry speci- 
mens broken after having been dried averaged 1,008 pounds per 
square inch. 

It will be seen, then, that these specimens when tested wet de- 



Art. 20.] COEFFICIENT OF ELASTICITY AND RESISTANCE. 



83 



veloped less strength than when tested dry, but surpassed the dry 
specimens after having been dried. 

Table V. is taken from a paper read before the American Sec- 
tion of the International Association for Testing Materials by 
Professor W. K. Hatt at the annual meeting, 1902, and shows 
the values of the tensile coefficient of elasticity of concrete bars. 







TABLE V. 




Number of Bar 


Age in Days 


Coefficient of Elasticity 
in Lbs. per Sq. In. 


Ultimate Tensile Strength 
in Lbs. per Sq. In. 


I 


35 
33 
28 
26 


2,700,000 
2,400,000 
1,400,000 
1,900,000 


300 


2 


305 


3 


360 


4 


280 







The size of the specimens was 4x4 inches square, and the elonga- 
tions were measured on a length of 17^ inches, although the 
specimens were about 30 inches long. The values of the ulti- 
mate strength as given are not very satisfactory, as many of tlie 
bars broke in the head; but Professor Hatt believes that the 
strength of the body of the bars was not different from the loads 
recorded at the point of rupture of the heads. The mixture was 



TABLE VL 



Number 
of Bar 



Composition 



2:4 Stone. . 
2:4 Stone. . 
2:4 Stone. . 
2:4 Stone. . 
2:4 Cinder. 
2:4 Cinder. 
2:4 Cinder. 
5 GraveL . . 



Age 

in 

Days 



9 
9 
14 
14 
9 
9 
7 
6 



Compressive 

Coefficient of 

Elasticity in 

Lbs. per Sq. In. 



4,702,000 

3,940,000 

4,340,000 

3,680,000 

558,600 

553,000 

630,000 

2,088,000 



Determined 
At a Compressive 

Stress of 
Lbs. per Sq. In. 



750 
1500 

750 
1500 



Ultimate 

Crushing 

Strength in 

Lbs. per Sq. In. 



2880 

2880 

2575 

2575 

495 

595 

416 

1 185 



composed of i part Peninsular Portland cement and 2 parts of 
clean, sharp pit sand, of which 84 per cent, was retained on a 
No. 30 sieve, and 4 parts of broken limestone, all of which passed 
through a one-inch sieve and of which 75 per cent, was retained 
on a ^-inch sieve. 

The coefficient of elasticity was computed with regard to the 



84 



TENSILE PROPERTIES, 



[Ch. V. 



set experienced after previous loads; in other words, it is the 
''elastic" modulus of elasticity. 

Table VL furnishes values of the compressive coefficient of 
elasticity for concrete cylinders 12 inches high and 8 inches in 
diameter, also reported by Professor Hatt in the same paper. 

In addition to the concrete mixture noted above, tests were 
made on a 1:2:4 cinder concrete and a i :5 gravel concrete, the 
gravel being a good quality of coarse gravel. The intensity of 
stress at which the compressive coefhcient of elasticity was com- 
puted is shown in the table. 

These experiments show the coefficient for compression to be 
considerably larger than for tension, but Professor Hatt has 
lately (Western Society of Engineers, 1904,) published the re- 
sults of a greater number of tests, and he states definitely that he 
finds no appreciable difference between the two moduli. Table 
VIL, taken from the latter paper, is otherwise self-explanatory; 









TABLE 


VII. 








Kind of Concrete.— Parts of 


Age 

in 

Days 


Coefficient of Elasticity 
in Lbs. per Sq In. 


Ultimate Strength 
in Lbs. per Sq. In. 


Cement 


Sand 


Broken 
Stone 


Gravel 


Com- 
pression 


Tension 


Com- 
pression 


Tension 


I 

I 
I 
I 


2 
2 


3 
3 




90 
28 
90 
28 


4,610,000 
3,330,000 
4,800,000 
4,130,000 


5,460,000 
3,800,000 
4,310,000 
4,320,000 


2413 
2290 
2804 
2403 


339 

237 
290 
233 




3 
3 











the results being averages of thirty-seven compression and twen- 
ty-seven tension specimens; the broken stone was limestone, 
being the product of the crusher below i inch, and the gravel ex- 
cellent pit gravel, including sand and pebbles. The concrete was 
mixed medium wet. 

The following tests on the tensile strength and the tensile co- 
efficient of elasticity of concrete were made in the Mechanical 
Laboratory of the Department of Civil Engineering of Columbia 
University under the author's supervision by Walter T. Derleth 
and John Hawkesworth, graduating students of the fourth class 
in civil engineering. The work was begun early in 1903 and 
lasted until the first part of June, 1904. The cement which was 



Art. 20.] COEFFICIENT OF ELASTICITY AND RESISTANCE. 



85 



used was Atlas Portland, upon which the usual acceptance tests 
were made. 

As determined by the Gillmore needle, the initial set took place 
in I hour and 45 minutes, and the final set in 3 hours and 50 
minutes. The strength of the neat cement briquettes, gauged 
with 13 per cent, of water, averaged 508 pounds per square inch 
at the end of 48 hours, 595 pounds per square inch at the end of 
7 days, and 849 pounds per square inch at the end of 28 days. 
Mortar briquettes of one cement to one normal sand, gauged 
with 1 1.3 per cent, of water, averaged 583 pounds per square 
inch at the end of 7 days and 671 pounds per square inch at the 
end of 28 days. Mortar briquettes, one cement to three normal 
sand, gauged with about 8 per cent, of water, averaged 148 
pounds per square inch at the end of 7 days and 203 pounds per 
square inch at the end of 28 days. 

The sand which was used in making the concrete was Cow 
Bay, and was clean and sharp. Its fineness, as tested by stand- 
ard sieves, was as follows: 



Retained by No. 2 sieve 

3 '' 

4 " . 
20 " , 

30 " . 

50 " . 

Passed " '' 50 " , 



0.49% 
1.15% 
6.68% 

9.52% 

15.55% 
38.90% 

27.7% 



The percentage of voids in the sand was determined to be 40.5 
per cent. The stone which was used for the concrete was a blue 
limestone, broken into sharp, angular pieces, varying in dimen- 
sions from 3 inches to \ inch. The percentage of voids, deter- 
mined by an average of two tests, was 48.1 per cent. All the 
concrete for the tests was composed of one part of cement to 
three parts of sand and five parts of broken stone, by volume; 
and these ratios by volume correspond very closely to the actual 
weights of the different constituents used in the mixture. Each 
specimen or bar contained about i| cubic feet of concrete, and 
each was prepared separately from a batch of the materials 



86 TENSILE PROPERTIES, [Ch. V. 

which averaged about i^ cubic feet. The sand and cement were 
Hrst thoroughly mixed dry and then the moistened broken stone 
was added, the whole being turned several times before the ad- 
dition of water. Water was then slowly added while the ma- 
terial was being turned over by shovels until its consistency was 
very plastic. The concrete was then deposited in the wooden 
moulds and lightly rammed into place with a wooden rod. After 
the first five bars had been moulded, it was found better to make 
the mixture so fluid that very little tamping was necessary; its 
consistency was then what is known as 'Very wet concrete." 

The moulds were always well moistened, and also greased with 
soft soap, before depositing the concrete, and no trouble was 
experienced in removing the bars from the moulds. The pins 
were covered with paraffined paper, so that they were easily 
withdrawn after the specimen had set. It was found imprac- 
ticable to remove the specimens from the moulds before four or 
five days. Specimens Nos. 2, 3 and 4 broke during the manu- 
facture, due to improper handling or too early removal from the 
moulds. In order to strengthen the heads of the specimens in 
the neighborhood of the pins through which the tensile pressure 
was later applied looped pieces of iron telegraph wire or heavy- 
weight picture wire were inserted. 

The shape of the specimens is clearly shown in the following 
figure, the cross section of each piece being 6x6 inches and the 
diameter of the pin hole through the head being if inches. 




FIG. 3. 

For the purpose of measuring the stretch or decrease in length 
of these specimens, upon the application of loads, it was neces- 
sary to have built a special extensometer. This piece of appara- 
tus was made by T. Olsen & Co. of Philadelphia, and consisted 
of two frames which inclosed the specimen and which were 
firmly fastened to it at a distance apart of 25 inches; on opposite 





U^^^^F ' ^^^^1 






^^B 


mt{ ^M 






^H 








^Hi 


V I^^H s ?^^ 




■Hi 

■■ < 


L ^R ^^^^^K 


^B 'X^B^^^H 




H/li 


BH 






i^H ^ -fiifc 








■ J 


^^Hl ^^^H ^^M 




i JB 


^^^H UK/ 1 








Ki^. flu 


^1 ^'.y^H'l ^^1 






Bjj^^^H > -""^Ib 






l*^jp^ 


^^^H ft^HI 






^1 


IIEi^4i 


B/ flVIHI^H 


f fft 

M 


B 






Showing Method of Determining the Elastic Behavior of Concrete Bars, 6x6-Inches in Cross-Section, the 
Specimens, with Electric Extensometer Attached, being Mounted for Tension Experiments in the 
150,000 Pound Emery Testing Machine of Columbia University. In the Photographs, as Shown, 
the Test- Pieces Are Blocked Up with Wooden Wedges. The First Specimens Tested Were Hung 
from Heavy Steel Cables, with Looped Eyes, but a Second, and Better Method of Attachment, by 
Means of Parallel Side Plates, is Shown in the Right-Hand Figure. Enlarged Views of the Heads of 
the Specimens Are Shown Opposite Page 120. 



Art. 20.] COEFFICIENT OF ELASTICITY AND RESISTANCE, 87 

sides of the upper frame were fastened two brass rods held in 
ball-and-socket joints; by means of micrometer screws these 
made electrical contact with two contact plates, which were in 
turn fastenend to the lower frame. Two rods, one on each side 
of the specimen, were used in order to guard against errors of 
observation and to eliminate errors due to bending cf the speci- 
men. The micrometer screws had a pitch of 1-40 of an inch, and 

I 



M t 



FIG. 4. 

the micrometer head was divided into 250 parts, so that each 
division of the head represented .0001 of an inch. It was found 
impracticable to measure smaller parts than one division of the 
head. The accuracy of the screws was tested by means of a 
dividing engine in the laboratory of the Physics Department of 
Columbia University, and was found to be exact for the range of 
testing for w^hich the instrument was designed. 

Tests were also made upon concrete bars of the same form 
which were reinforced by wrought-iron bars, and it will be con- 
venient to record at this point the results of tests made upon 
these wrought-iron bars. 

Three bars were tested — one J of an inch square, which de- 
veloped an ultimate resistance of 48,700 pounds per square inch, 
with a coefficient of elasticity of 29,620,000; one bar ^ inch 
square showed an ultimate resistance of 54,800 pounds per 
square inch and a coefficient of elasticity of 29,900,000, and one 
bar f of an inch square had an ultimate resistance of 52,275 
pounds per square inch and a coefficient of elasticity of 27,- 
590,000, 

Failure of the specimens, in the tensile tests, occurred in all 
cases but two, in the head, on each side of the pin hole. The 
wires imbedded in the head were not broken, but had slipped 



88 



TENSILE PROPERTIES. 



[Ch. V. 



in the concrete. The ultimate tensile resistances are therefore 
not of any value; the stress conditions at the pins in members of 
this shape are so peculiar that in future it will be well to devise 
some other method of applying the stress than the one which was 
used. In the compression tests none of the specimens was 



Sp 



Ult 






ciiiiei No. 5 
: 138 days. 



"El^ 



Stic Limit 



Load 



Flajn Concrete 
Length ; 25" 
Section rbfx 6M 



AreaTT -^pio" 
Areaa'tPin--32i'5° 



.Resist., Body 876 Ibs.per sq.m. 
Pin 1000 « " 

«0 <•!. 



Ibs.per sq.in. Coefficient 

0-30|0 
300-5(J0 



500-600 




of Elasticity 
2860000 lbs. per sq.in. 
2665000 « i< 
'25OU0OO a t 



FIG. 5. 



stressed to such an extent as to cause failure in the body of the 
bar; failure occurred generally by crushing or shearing at the 
heads or at the pin holes, but was usually accompanied by fine 
cracks appearing generally over the entire surface, so that the 



Art. 20.] COEFFICIENT OF ELASTICITY AND RESISTANCE. 



89 





Age: 


132 da^s. 










Load 
per 


in lbs. 
sq.in. 

40 












Coeff 


Ult.I 
cient ( 


esist., Body 

at Fin 

f Elas^ticity 


37 lbs.] 
i2 " 
120000^ 


Der sq.i 
) 


a. 






30 




/ / 




a 




S 


















20 


1/ 


/ 




03 




u 

C 


















10 


■''/ 


> 








Strain 
per lii 

.0009 


§ 

o 
o 


o 
o 


g 


o 
o 


i 


§ 

o 
o 


1 


o 
o 
o 




f 




























J 


50 


o 


o 
o 


i 






A 


ge: 140 


Speci 
days. 


jien N 
Leu 
Sec 


0. 6 
gth 
ion 


6 X t 


%" 




Jl 


100 


















Are 
Are 


1 

I at Pi 


38Jau. 
i33>^^ 


1 




fi 
i' 
1' i 


150 










Compressibn: 
Ult.ResistJ, Body 
at Pin 


8121b 
925 


s.per sq 


.in. 








in 

! 1 


200 










Elastic Limit 
Load 
Ibs.per sq.in. 


450 
Coef 


icient 


[)f Ela! 


iticity 




// 


/ 

1 
1 
1 


250 










0- 
300- 
500- 


300 
500 
600 






2070000 « 

1850000 

1735000 


yn" 




r ' 

1 1 


t 

1 

1 


300 


























1 1 

r 1 

1 


• 


350 


























1 

r 


5/ 


400 






ci 




















r 


1/ 


450 






CO 
















# 


'i 
i^ 


c 


11 


500 






a 
o 














.^ 


y/ 
f 


1^ 




t 


550 




















/ 


/6 

1 

1 


=? 


1/ 
^7 




SOO 


















/ 


/ 


1 

1 
1 

1 




/ 

/ 




650 
















y 


/ 


/ 
/ 


f 


/ 


/ 




700 














Y^ 


y 




/ 
/ 




/ 






750 











FIG. 6. 



ultimate resistance was very nearly developed. None of these 
considerations concerning methods of failure disturbs, however, 
the measurements of the elastic deformations. It should be 



90 



TENSILE PROPERTIES. 



[Ch. V. 



















Load 
per 


in lbs. 
sq.in. 














Age: 


125 da 


rs. 












50 












Coeffi 


Ult.E 
cient ( 


esist., 
Si Elas 


Body 
t Pin 

ticity 


33 lbs. 
38 ' 
llSiOO 


per sq.i 
) lbs. p( 


r sq.in 






40 








C 






















30 


1 


/ 
1 


f 


CO 

C 






















20 


/ 


1 I 
1 / 


























10 


t'/ 










o 


o 

8 


t- 


o 




o 


i 


<N 


1 




r 










* S 


















1 


50 ^ 


i 

o 


o 


i 




1^ 


















/ 


100 










£ 


Ag 


;cimer 
;: 133 c 


.No. 8 
ays. 


Pla 

Lengt 
Sectic 


in CoE 
n 


Crete 
25.'/ 
6x6) 


i" 




/' 


150 


















Area 
Area at Pin 


3734 n'/ 
32V5°'' 




; 


7 i 


200 












Ult.Eesist., 

J ^J 
Elastic I 


Body 

tPin 

^imit 


686 lbs. per sq. 
•785 •' ■»« 
450 u t< 


In. 




/ / 
/ \ 


/ 
/ 


250 










.L 

Ibs.p 


oad 

er sq.in. 


Coefl 


icient 


jf Elai 


;ticity 


1 


/^ / 


/ 
/ 


300 










0- 
300- 
500- 


300 
500 
600 






1910000 lbs. per sq.in. / 
1900000 u » A 
1667000 .( « / 


/ 
1 


§/ 


350 






CO 

in 
















*1 


7 


1 -^ 

1 £5 


7 

r 


400 






O 














i 


c / 

V 








450 




















¥ 




^ / 

/ 
/ 


# 

«/ 




500 


















> 


/ 










550 
















nC 


/ 






/ 






600 









































FIG. 7. 



noted, however, that both kinds of stress, tension and compres- 
sion, were applied, in the order named, to every individual speci- 
men. This was done in order to eliminate from the results any 



Art. 20.] COEFFICIENT OF ELASTICITY AND RESISTANCE, 



91 



possibility of differences in the method of manufacture of the 
specimens, and that the elastic properties of the two kinds of 
stress might be directly compared. An objection might there- 
fore be lodged against the compression tests, since these suc- 
ceeded the tension tests; but, in the opinion of the author, none 
of the specimens was injuriously affected by the previous tests, 
principally because the tension tests failed at such low intensities. 
Table VIII., page 95, records the results of these experiments. 

After each whole specimen had been subjected to the com- 
pression test, parts of the same were then subjected tO' crushing 




FIG. 8. 



and to shearing tests. The manner of loading in the latter case 
is shown in Figure 4, page 87. 

It is the opinion of the author that the size of broken stone 
used in these tests was too large. In bars 6x6 inches in section 
3 inch stone is too large; it would have been preferable if 2 inch 
stone had been the limiting size. 

The stress-strain curves for specimens Nos. 5, 6, 8, 9, 11, 22 



92 



TENSILE PROPERTIES, 



[Ch. V. 



and 23 are shown- in Figures 5 to 1 1 respectively ; it will be seen 
that the curves for tension and compression are very nearly 
straight lines, with equal inclinations. 

Table IX., page 96, shows the results of tests made in the 
Laboratory of the Technical Institute of Vienna during 1891 and 
1892, and are recorded in the Transactions of the Austrian Soci- 
ety of Civil Engineers for 1895. 




Age: 120 
U^lt.R 



esist 



days. 
B 



)dy 33 lbs.per-sq.in. 



Pin 38 



Crtefficient of Elasticity 133()000 Ib's. per sq.in, 






Spe 
Age 



cimen No. 11 Plain Concrete 



123 days 



Length 
Secti jn 



25/; 
6x8^ 



Area 
Arealat Pin 



36%°" 
32'/,o:'^ 



Ult.Resist., Body 
Pin 



728 lbs. per sq. in. 
832 



„ Load 
lbs. per s q.ih. 

-1300 



Coefficient of Elasticity 



165500O'=^g" 



FIG. 9. 



The batch numbers marked Wa were left in water three 
months from the day of making, being removed three days be- 
fore the test; batch numbers marked Wb were left in water the 
entire time. 

The table gives the ultimate compressive resistance of 4 inch 
cubes and of 3^x3^x10 inch prisms. The strains experienced by 
the latter- were also measured, so that it was possible to obtain 
values of the coefficient of elasticity. The table also gives values 



Art. 20.] COEFFICIENT OF ELASTICITY AND RESISTANCE, 



93 



















Load 
pel' 


in lbs. 
sq.in. 














Age: 


111 da 


.'S. 












50 








S 

-1 






Ult.Resist., 


Body 
Pin 

" ■ 


43 Ibsi 
49 - " 


aer sq.i. 

li- 


i^ 






40 




/ 


/ 

/ 


-Ji 

33 
H 




Coeffi 


cient ( 


)t Elas 


ticity 


880000 ] 


bs, per 


sq.in. 






30 


/ 


f 

/ 


■ / 


/ 




a} 

<0 


















20 


I 
/ 


/ 
// 


/ 
























10 


U 


7 








ill 

30 O 


00 

o 
o 


1 

o 


to 


2 


i 


CO 


0* 


•H 




^ 




























/ 


o 
50 ^ 


1 


to 
o 
o 
o 

o 


00 

o 






Ag 


jciiuer 
;: 117 c 


iNo. 2 
ays. 


2 Plain Co 
Length 
Section 


icrete 
25- 
6x65 


<' 




/ 


100 


















Area | 
Area at Pin 

1 


38M^' 




/ 


/ 


150 












Ult.Resist., 
Elastic : 


Body 
Pin 

Jinit 


587 lbs. per sq.in, 

612 

iOO 




/ 


1 


200 










1u ^ 

lbs pel 


ad- 
' sq.ini 




Coef 


icient 


of Elasticity 




/ 


/ 


250 










0- 

300- 


300 
500 






1390000 Ibs.per sq.in. 
1258Q0P « u 


/, 


/ 

r 


1 

/ 


300 






^ 
















/ 


/ ■ 




/ 

1 


350 






■j: 














/ 


/. 


/ 
/ 




/ 

/ 


400 






5 












^ 


/ 


/ 

/ 
/ 
/ 




4 

1 

/ 


r 


450 
















^ 




/ 
/ 






/ 

9 

/ 




500 


















y 
X 






/ 






550 






























600 









































FIG. 10. 



of the ultimate resistance and the coefficient of elasticity of con- 
crete and mortar specimens in tension. It was found that the 
concrete prisms had permanent sets at relatively low stresses. 



94 



TENSILE PROPERTIES. 



[Ch. V. 




FIG. 11. 



The report states that the total strain in both tension and com- 
pression was nearly always proportional to the loadings, but that 
this cannot be set down as a rule. Nor could the tests decide 



Art. 20.] COEFFICIENT OF ELASTICITY AND RESISTANCE. 



95 





kO 


M 


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NH 


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In Lbs. 
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5'C 


1 1 1 1 1 


1 


1 1 1 




c> o 


U' 00 CN — VO 


TO JT 


1 1 1 i 1 


1 


1 1 1 




VJT JX 


1 00 ' VI crv42>. vj' 


















ft -T 
CO » 


1 1 1 1 1 


1 1 


1 1 1 




1—1 — 


«,-„„- 


At Age of 










to to 


vjT w C^ GN C^ 


Hflwc 
























1 










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^ ^ 


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xja 


7- 


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DO 

r 
m 



96 



TENSILE PROPERTIES. 



[Ch. V. 





o 


o o 


o 


o 


o 


o 


o 


o 


O 




o 


o o 


o 


o 


o 


o 


o 


o 


O 


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o 


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o 


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o 


o 


o 


o 


o 


XjpijsBigiojuaiD 






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00 


V£) 00 


00 — ■ 


-iJJ303 33BJ3AV 




•^^ 


CO 


CO 


(^ 


»r\ o 


^ 


(N 




in r^ "^ 


'-' 


(N 


Cl^ 


CO iO 


kfNvO 


•aj "bg J3d "sqq 


t^ 


^o 


G\ cn 


Tf - 


tN 


TT 


CO 


iTs 


a; 33UBJSIS0JI 


-r 




f-^ 


00 


»rv ri »rN fsi 


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CO 


c^ c<^ 


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o o o 

o o o 

o o o 

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r^ r^ CO 

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o 
o 

o 



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o 
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IC 



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00 CO. 

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sq^uovv UI dSy 



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CO) CO CO 1—1 1—1 



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(N <N r« 



t^ CO 
— nj 



O CO 

1—1 CO 



•UI -bg J3d 'sq-] 

UI SOUBlSjSS^ 
•Jlfl 33BJ3AY 



00 in 00 

c> o in 

\D '^ 0\ 
CO CS <N 



CN CO 

in -^ 
« n» 



— 00 

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CO CO 



sqiuow ui agy 



susmpsdg 
JO aaqmni^ 



•on qojBg 



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C3 






o o 
o o 

in^ 
in CO 

CO tT 



<T\ 00 
in <N 

00 "^t- 

cs CO 






n» " 

O* CO 



^^ 



o o 
o o 
o_o 

tC in 

FN \D 

1-1 ^ 



in r< 

00 i-H 

<N CO 



CO CO 



in t^ 
00 c-^ 
CO \D 

CO CO 






C 

a 
CO 

S c 

W G5 
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c 

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c 



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a> 



c 

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— ' r* CO .-I i-i i-» 



T3 

C3 

C 

CJc/3 
«-» CO 



Art. 20.] COEFFICIENT OF ELASTICITY AND RESISTANCE. 97 

definitely whether the coefficient of elasticity for tension or com- 
pression differed. It will be seen in these experiments that the 
A^alues of the coefficients of elasticity decrease as the proportions 
of other materials to sand increase, and that as the ultimate 
strength of the mixture increases so does the coefficient of elas- 
ticity. It is not clearly stated whether the values are the elastic 
values of the coefficients; it must be so inferred. 



Tensile Properties. 

Conclusions. 

From the foregoing experiments it is possible to draw the fol- 
lowing conclusions : 

First. Concrete in tension appears to possess no point which 
might be termed the elastic limit; in other words, the coefficient 
of elasticity is a constant quantity from a condition of no stress 
to the point of rupture. 

Second. The coefficient of elasticity appears to increase with 
the ultimate tensile strength of the material, but, due to the great 
difficulty in determining the actual breaking loads of concrete 
bars in tension, it seems impossible to connect in any rational 
manner the coefficients with the breaking loads. 

Third. The ultimate tensile resistance varies in some manner 
with the richness of the mixture and with the age of the speci- 
men, but it appears impossible to determine any expression which 
will present rationally the relation of these quantities to one 
another. 

It is only possible to say that the value of the elastic or true 
coefficient of elasticity has been found to vary between 1,000,000 
and 5,000,000 pounds per square inch, and that the ultimate ten- 
sile resistance varies from 100 to 500 pounds per square inch. 

It will be seen later that it appears possible to connect the 
ultimate crushing resistance of concrete with the compressive co- 
efficient of elasticity, and since it has previously been shown that 
the ratio between ultimate tensile and compressive resistance is 
about as 1:10, it may be possible to transpose to tension the 
empiric relations deduced in the compression experiments by in- 



98 TENSILE PROPERTIES. [Ch. V. 

serting in those expressions, in the proper manner, the ratio of 
I to lO. 

From the experiments that have been recorded so far, antl 
from those which will be shown for compression, it may be said 
without much error that the coefficients for both tension and 
compression for any one mixture may always be taken equal. 
This will indicate the manner in which the ratio of i to lo must 
be used. 



CHAPTER VI. 
COMPRESSIVE PROPERTIES. 

Art. 21. — Coefficient of Elasticity and Ultimate Resistance. 

Professor C. Bach of Stuttgart has made perhaps the most in- 
teresting and most reHable of experiments on the compressive 
elasticity of cement and cement mixtures. His experiments on 
the elasticity of concrete have been published in the "Zeitschrift 
des Vereines Deutscher Ingenieure" for April 27, 1895, and No- 
vember 28, 1896. 

The experiments recorded in the first issue mentioned were 
made by Professor Bach in July, 1894, on 32 cylinders with a 
circular cross section having a diameter of 9.9 inches and a 
height of 39.4 inches. Six different proportions of ingredients 
were used, and in general six specimens were made of each mix- 
ture, three with one brand of cement and three with another 
brand. The following table shows the mixtures employed, the 
parts being expressed by volume: 

I. I cement, 2J Neckar sand, 5 Neckar gravel. 

n. I cement, 2J Neckar sand, 5 limestone shingle. 

HI. I cement, 7 J natural gravel and sand mixed. 

IV. I cement, 3 Neckar sand, 6 Neckar gravel. 

V. I cement, 3 Neckar sand, 6 limestone shingle. 

VI. I cement, 9 natural gravel and sand mixed. 

The ends of the specimens were plastered with a layer of neat 
cement in order to facilitate planing. The specimens were taken 
from the moulds at the end of one day, and were then covered 
with bagging, which was kept moistened, for 28 days. At the 
time of testing the age of the specimens varied from yd to 97 
days. 



Lof 



100 



COMPRESSIVE PROPERTIES, 



[Ch. VI. 



The deformations were measured by means of a specially de- 
signed instrument reading directly to .00013 inch, on a meas- 
ured length of about 29 inches. The load was applied to the 
specimens at a steady rate, from o to the point desired, in i^ min- 
utes, and the removal of the load was accomplished at the same 
rate. 

In all of Professor Bach's experiments the loads were added 
and removed until it was found that there was no change in the 



TABLE I. 



Composition in Parts by 
Volume 


CO 

c 


.5 

w 

OS 

< 


Cement Used— Brand "B" 


H 

o 

B 

u 

< 


Cement Used— Brand "L" 


e 
w 

E 

u 




u 

s 



■0 

c 


"Si 
a 

u 
1 
u 


> 
as 
u 

a 

Sj 



u 


73 

C 

e 

M 

> u 


*> 



*o 
u 
a 


Coefficient of 

Elasticity 
Between Inten- 
sities of Stress 
of and 113 
Lbs. in Lbs. 
per Sq. In. 


4> 

.2 ry 

OS S; 
« a 
2 « 

5.5 


'> 
2 
O 

o 

'o 

u 
o. 


Coefficient of [^ 

Elasticity ^ ,S 

Between In- u-S • 

tensities of 0,U «co 

and 113 Lbs.l « c u 

inLbs |2S. 

perSq. In. .5--^ 

DOiJ 




2>^ 

2>^ 

3 
3 
3 
3 
3 
3 


5 
5 
5 

6 
6 
6 


5 


7M 
7>^ 

6 
6 
6 

9 
9 
9 


2>^ 

2>^ 

2>^ 

2>^ 

2/2 

3 

3 

2>^ 

2^ 

3 

2>^ 

2>^ 

3 

2>^ 

3 

3 


2.37 

2.42 
2.42 
2.43 
2.39 
2.42 
2.40 
2.39 
2.39 
2.39 
2.43 
2.43 
2.42 
2.42 
2.40 
2.41 


4,340,000 
4,670,000 
5,340,000 
4,730,000 
4,870,000 
4,970,000 
4,480,000 
4,470,000 
4,200,000 
4,180,000 
4,910,000 
4,640,000 
4,470,000 
4,270,000 
4,530,000 
5,170,000 


1370 
1780 
1980 
1800 
1 865 
2000 
2090 
1640 
1560 
1700 
1680 
1720 
1640 
I5I0 
1660 
I960 


2/2 

2/ 

3 

3 

2>^ 

3 

3 

2>^ 

3 

3 

2^ 

2X 

3 

2>^ 

3 

3 


2.33 
2.44 
2.46 
2.45 
2.33 
2.34 
2.35 
2.37 
2.38 
2.38 
2.46 
2.43 
2.45 
2.34 
2.33 
2.34 


3,410,000 
5,160,000 
4,950,000 
4,760,000 
3,820,000 
3,450,000 
3,480,000 
3,920,000 
3,680,000 
3,910,000 
4,170,000 
4,190,000 
4,170,000 
3,610,000 
3,250,000 
3,220,000 


880 
1520 
1580 
I6I5 
1230 
1200 
1280 
1090 
1000 
1080 
1240 
1360 
1230 
960 
908 
915 



deformation as found by a previous reading. This required, in 
general, when the applied load was less than 570 pounds per 
square inch, four to eight repetitions; but with higher intensities 
of stress the deformations of the specimen were found to be also 
dependent on the time which the load remained on the specimen ; 
that is, the strain was a function of both the load and the length 
of time the load was applied. This agrees with experiments 
made on some other materials, more notably those made by Pro- 



Art. 21.] COEFFICIENT OF ELASTICITY AND RESISTANCE. 



101 



X X X X xxxxxxxxx:;:n<<<<<:p-::::- 




102 COMPRESSIVE PROPEm'lES, [Ch. VI. 

fessor Thurston. This question is of the greatest interest in con- 
nection with the fatigue of materials. Table I. shows the results 
obtained. 

The second set of experiments, which were recorded by Pro- 
fessor Bach in the issue of the 28th of November, 1896, were 
made on two sizes of round cylindrical specimens, the first being 
39.4 inches high, with a diameter of 9.9 inches, and a consequent 
cross section of yy\ square inches; the second being cylinders 
of the same cross section, but only 9.9 inches high. The experi- 
ments on the elasticity of the material were made only on the 
larger specimens, the deformations being measured on a length 
of about 29J inches, by the same instrument noted before, read- 
ing directly to .00013 inch. Loads were applied at intervals 
of 112 pounds per square inch. The average age of the speci- 
mens at the time of testing was about three months. The con- 
crete was prepared as nearly as possible in the same way as in 
the case of actual construction work; water was added in such 
quantities that by ramming the whole mass appeared very plastic. 

Table II. shows in detail the proportions of the mixtures em- 
ployed and the number of specimens tested, the total number 
being 102. 

The sand marked ''Egginger" was quartz sand with a little 
feldspar, while the "Danube" sand was river sand. It will be 
seen that in almost all cases the concrete in which the stone was 
a limestone attained a higher ultimate resistance to crushing. It 
would seem, then, that the gravel concrete should be the more 
elastic; that is to say, it should yield more under stress than the 
limestone concrete; the table shows this to be so. Table 11. also 
shows clearly the increase and decrease in the coefficient of elas- 
ticity with the variation of cement in the mixtures. 

Figure i is plotted from the results of the table and shows the 
variation in the coefficient of elasticity with varying proportions 
of cement to other aggregates. In the case of mortar, it will be 
seen that the coefficient rises from the neat cement to a mortar of 
one cement to one sand, and then slowly drops until, with a mix- 
ture of one cement to three and one-half sand, it is about the 
same as that for neat cement. The results as plotted for the 



Art. 21.] COEFFICIENT OF ELASTICITY AND RESISTANCE, 



103 




1:2 1:4 1:6 1.8 1:10 1:12 1:U 
Propoition of Ceiuent to Aggregate 

FIG. 1.— BACH'S TESTS. 



limestone and gravel concretes show a steady decrease in the co- 
efficients as the ratio between cement to aggregate increases. 
The latter results in the case of the concretes are perhaps to be 
expected, since it seems rea- 
sonable to suppose that a ma- 
terial whose strength depends 
on cement will be yielding in |H. 
proportion to the quantity of 
cement in it. 

Professor Bach quotes ex- 
periments by Hartig, in ''Civil 
Ingenieur," 1893, page 467, 
and Baker, in ''Civil Inge- 
nieur," 1894, page 718, as fur- 
nishing results corroborating the variation of the elasticity as 
found by him. 

The coincidence in the rise of the values of the coefficient of 

2000 

1900 

1800 

1700 
^.1600 
": 1500 
^1100 
S.1300 
;31200 
.S 1100 

iiooo 

u 

^ 900 

<o 

•S 800 
2 700 

Pi 

S 600 
o 

^ 500 
iOO 
300 
200 
100 









































Failed at 1960-1 


bs. 




X 








^ 


-^ 




" ' 








/ 








y^ 


^^^ 










/ 


/ 






/ 


^' 












/ 








/ / 


'" 












1 






/ 


y 














/ 






/A 


/ 














/ 




-v" 


// 
















/ 




4A 


/ 
















I 




i// 








r 1 Cement 

Concrete] 9 sand+ Gravel 

Age about 3 Months 

Cylinder 9!'8 Diameter^ 

39:'4 High ) 

Reported by Bach. 

Zeitsch. Ver.Deutsh.lng 
April 27, 1895 




i 


.t// 










[ 


£( 


y 










\ 


W 












r 


// 












1 y 


u 

/ 












/ 






















/ 






















/ 






















/ 























3 i 5 C 7 8 

Decrease in Length per Inch of Specimen in .0001 Ins. 
FIG. 2. 



10 



elasticity as compared to the increase in the specific gravity of 
the material is worth noting, and the table shows clearly that in- 



104 



COMPRESSIVE PROPERTIES. 



[Ch. VI. 



creased power to resist distortion accompanies higher specific 
gravities. 

Figure 2 is the only stress-strain diagram inserted illustrative 
of Professor Bach's results, because it is so thoroughly char- 
acteristic of all the results obtained. It shows completely the 
behavior of the material almost to the point of failure. The 
elastic strain curve differs but little from a straight line for the 
first half of its length ; and that this curve never shows great de- 
partures may be seen from the following average values of the 
coefficient of elasticity which Professor Bach has deduced from 
the preceding experiments: 



Mixture as Given by Colnmn Headed 
"Specimen Marli" in Table II. 



I., V Neat Cement 



II I : I >^ Mortar 



III 1:3 Mortar 



IV I -AYz Mortar 



VI* 1:2^:5 Concrete 



VIII* 1 :3:6 Concrete 



xvr 



1:5:10 Concrete 



Vllt I:2>^:5 Concrete 



IXt 1:3:6 Concrete 



XVIIt 1:5:10 Concrete 



Stress-Strain Relation^ Expressed in 
Lbs. per Sq. In., from Equation 
pn 



3,556,000 = 
5,050,000 = 



T 



4,480,000 = -y- 
3,270,000 = -y 



4,230,000 = 



3,980,000 = 



,1.16 



3,080,000 = -^ 



,1.16 



6,500,000 = -^ 



5,400,000 = -'^- 



5,210,000 = ^- 



*Gravel Concrete. tLimestone Concrete. 



Art. 21.] COEFFICIENT OF ELASTICITY AND RESISTANCE, 1 05 



As shown, the value of the constant E in the Bach equation in- 
creases over that calculated in Table II. in the same sense as the 
exponent n ; that is, if n increases, so does the value of E, as 
compared to its value when n equals one. It seems to the author 
that Bach's refinement is unnecessary. It has never been found 
necessary to express the stress-strain relation of a material like 
steel by an algebraic expression covering the entire range of 
stress, and it will be shown that concrete possesses an elastic 

TABLE III. 
COMPRESSIVE STRENGTH OF NEAT DYCKERHOFF CEMENT. 



Size of Specimen 



Crushing Load 
in Lbs. per Sq. In. 



1 Inch Cube, 

2 " " . 

3 " 

4 " 
3 " 

6 " 

7 " 

8 " 

9 " 

10 " " . 

11 " 

12 " " . 
4x 
4x 
4x 
8 



4x 
4x 



8 

8 

8 

8 
12 
12 

12 X 
12 X 



I, 

2. 

4x3. 

8x2. 

8x3. 

8x4. 

8x5. 

8x6. 
12 x2. 
12x4- 
I2x 6. 
12 x8. 



3896 

7094 

3937 

4847 

4610 

4283 

4987 

3007 

4734 

4761 

3374 

3291 
1 647 1 

6370 

6003 
10664 

7186 

3932 

6019 

3771 

Tested in built-up 
I piers, set dry. Re- 
I suits not compara- 
ble. 



Average Modulus of 

Elasticity 
in Lbs. per Sq. In. 



1,338,774 
1,421,111 
1,310,416 
1,703,877 
1,633,107 



limit, although not a precise one, below which the stress-strain 
relation may be expressed by a constant. 

General Q. A. Gillmore treats very extensively of the com- 
pressive resistance and elasticity of Portland and natural cement 
mixtures in his book, ''Notes on the Compressive Resistance of 
Free Stone," etc., published in i888. The accuracy of the tests 
appears to be insured, since they were all made at the Water- 
town Arsenal. 



106 COMPRESSIVE PROPERTIES. [Ch. VL 

In the case of the neat cement experiments, abstracted in 
Table III., a series of cubes and prisms was made of Dyckerhoff 
Portland cement, the average age of the specimens at the time 
of testing being one year, ten and one-half months. The cubes 
varied in sizes, by increments of one inch, from one to twelve 
inches on the side, there being six samples of each size. The ma- 
jority of the specimens which were tested, including both the 
cubes and prisms, had plastered faces, the exceptions being a few 
of the 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11 inch cubes. It should be 
noted that plastering the compressed surfaces uniformly increases 
the ultimate resistance. 

It will be seen that in the case of the cubes the smaller cubes 
gave slightly higher crushing resistances than the others ; that in 
the case of the prisms the very flat prisms furnished extremely 
high values. This is to be expected. It will be seen that the 
average value is about 5,000 pounds per square inch. The co- 
efficient of elasticity was determined for the larger cubes, and in 
calculating these values General Gillmore divided the unit stress 
at a point which he names the elastic limit by the unit deforma- 
tion, no deduction being made for permanent set; these coeffi- 
cients, therefore, are not the true elastic coefficients; they would 
be greater than given in the table. 

Figure 3 shows the stress-strain curve determined for one 10- 
inch cube, and also for one 12-inch cube. The curves are char- 
acteristic of all the tests, although some show a slight convexity 
to a horizontal line at the origin. This may possibly be due to 
the squeezing out of the plaster between the specimen and the 
bed plate, since it seems that the deformations were measured 
between the heads of the testing machine. The majority of the 
curves shown by General Gillmore are, however, very similar to 
Figure 3. The elastic limit might be placed at .6 to .75 of the 
ultimate resistance. 

Table IV. gives the values of the ultimate resistance obtained 
by General Gillmore for mortar and concrete cubes mixed with 
three different brands of cement — two natural and one Portland. 
Each result shown is an average of two specimens, the beds of 
all specimens being plastered before being tested. Some of the 



Art. 21.] COEFFICIENT OF ELASTICITY AND RESISTANCE, 



107 



Total Load on Specimen in Pounas 



P 

*l 

O 



Q 

r 

o 

pn 




108 



COMPRESSIVE PROPERTIES, 



[Ch. VI. 



cubes were, in addition, placed between wooden pine cushions, 
but it was invariably found that the use of these wooden cushions 
did not develop the full possible strength of the material. 

In the table as given no distinction has been made between 
specimens, whether they were provided with such cushions or 
not. The coefficient of elasticity could only be determined for 



300,000 




I JBrpk ^J^, 215; 



mvM. 



Norton's Cement 

1:3:6 Mixture 

le'Cube 



IT 



M 
Brollce at 320,000 Lb* 



Mortar .1: IX 

Norton's Cement 

le" Cube 



BrcU^at3T9,?00Lt)C. 



300,000 



100,000 



Norton's Cement 

nrH r6 Concrete 

16 "Cube 



.OL 



.02 .03 .O*- .W 

Decrease in Total Length in Inches 

FIG. 4.— FROM GILLMORE'S TESTS. 



.06 



those specimens in which no wooden blocks were used, because 
the deformations were measured directly between the heads of 
the testing machine and the concrete was forced rather deeply 
into the wooden cushions. 

The values shown have this peculiarity: that the concretes 
seem to possess, on the whole, a greater strength than the mor- 
tars, which is rather exceptional, and can perhaps be explained 
only by the fact that the mixtures were better balanced. 

Table V. shows the values of the coefficients of elasticity of 
the larger size cubes, determined in the same manner as in the 



Art. 21.] COEFFICIENT OF ELASTICITY AND RESISTANCE, 



109 



S 



Total Compressive Load in Poimds 



s 



s 



s 



2 
P 

•l ^ 

I n 

» - b 

H & 
m * 

H 



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\ 


















o^S ^ 






V 
























\ 










1 








^ CO C! 






^ 










1c 








05. 3 






\ 


















c+ 






\ 










IW 
















\ 










'o 
















\ 










pr 


























<6 


















w 








^ 












































g- o. 








CC 


















. s °° 








h^ 


















I p 








O 












































\ -^ 








« 


















I **^ 








fl 


























rr- 


















\o 








* 












































Vo 


























it^ 


























F 











no 



COMPRESSIVE PROPERTIES. 



[Ch. VI.. 



case of the neat specimens of Table III. The intensity of stress 
for which these coefficients are calculated is shown. 

Figures 4 and 5 are characteristic stress-strain curves of all 
the mortar and concrete tests. It will be seen that there is a 
point which might be called the elastic limit, although all the 

TABLE IV. 



£ 4> 



- - 1429 



Composition of Specimen 


Parts by Volume 






_ 


c 


Cement 


•a 

c 

C8 

CO 


it 
> 

a 






I (DryMeas.) 


3 


_ 


_ 


" 


3 


2 


4 


I (Paste) 


1/2 


- 






3 


- 


- 




iVz 


- 


6 




3 


— 


6 




3 


- 


- 




3 


— 


6 



Size of Specimen Cubes 



2 


4 


1 
6 


8 


10 


12 


In. 


In. 


In. 


In. 


In. 


In. 



14 
In. 



16 
In. 



18 
In. 



Ultimate Compressive Resistance in Lbs. per Sq. In. 



758 


800 


707 


945 


685 


715 


612 


1032 


II27 


1035 


1 167 


972 


723 


856 


2042 


1340 


1746 


— 


1346 


— 


1247 


1324 


750 


790 


— 


688 


— 


718 


2322 


963 


1434 


— 


1 560 


— 


1447 


1633 


1000 


861 


— 


765 


— 


843 


3450 


2655 


2469 


— 


2434 


— 


2519 


4014 


2629 


3025 


— 


2690 


— 


2978 



941 



A— Newark Co.'s Rosendale; tested at age of about 22 months. 

B — Norton's Natural; tested at age of about 3 years and 10 months. 

C — National Portland; tested at age of about 3 years and 10 months. 

Specimens show considerable permanent deformations at faii-Iy 
low stresses. This elastic limit might be taken between two- 
thirds and three-quarters of the ultimate resistance. None of 



TABLE V. 



Brand of 
Cement 



Newark ) 
Rosendale ) 
Norton's Nat. 



National Port. 



Composition of 
Specimens 



U 



3 
3 

I'A 

3 
3 
3 



Stone 



( 2 Gravel ) 
14 Stone ) 



Size of Specimen 



Cube 


8 In. 


10 In. 


12 In. 


16 In. 


18 In. 


Coefficient of Elasticity in Lbs. per Sq. In. 





549,000 


465,000 


572,000 






614,000 


655,000 






573,000 


484,000 






708,000 


778,000 






702,000 


530,000 


1,092,000 




1,606,000 


1,864,000 


1,076,000 




1,350,000 


1,732,000 



567,000 



■n "> •' • 

w =*- ? 
c Si 3^ 

— e O t-t 

u < a 

a J 



650 

750 
410 
800 
500 
1800 
1500 



the curves show the coefficient to be a constant quantity, and not 
much error is introduced if it is taken constant below the assumed 
elastic limit. 



Art. 21.] COEFFICIENT OF ELASTICITY AND RESISTANCE, 



111 



Table VI. gives the results of Henby's compression tests on 
stone concrete and cinder concrete, these tests having been made 
at the same time and in the same manner as the tension tests 
noted in Art. 20. 

TABLE VI. 
COMPRESSION TESTS— STONE CONCRETE. 



CO 

u 




Composition- 




e (u 




■»! 




CO c 






H 


CO 


Parts of 




^■tj 




jB, 


Modulus 


4> 






% 


n 




«- 




Treat- 


C.2 


of 
Elasticity 


coco 


Con- 




b 


^ 






Remarks 


1 

3 

Z 


.s 

u 

< 


c 
u 

w 
U 


T3 
C 
« 

CO 


4> 

c 



£5 


o*3 
« c 
•- 2 

COOT 


ment 


§c3 


Lbs. per 
Sq. In. 


•S CO 

55 


sistency 




220 


90 




2 


4 


A 


2 


Air dry 


140 


4,421,000 


1243 


Dry 




221 


90 




2 


4 




2 




144 


5,792,000 


982 


" 




80 


— 




2 


5 




2 


" 


146 


3,927,000 


726 


" 




272 


60 




3 


6 




2 


Air 





2,886,000 I 413 


Very dry 




225 


30 




2 


4 




1^2 


" 


160 


7,171,000 1 3020 


Plastic 




226 


30 




2 


4 




1^2 


Water 


152^ 


4,625 000 2610 


" 




76 


9 




2 


5 




1^2 


Air 


152 


4,930,000 


423 


" 




248 


32 


1 


2 


5 




1>^2 




151 


5,055,000 


2097 






249 


32 




2 


5 




1/2 


Water 


154^ 


7,292,000 


2830 


*' 




250 


34 




3 


6 




IH 


Air 


143 


5,104,000 


1310 


" 




251 


39 




3 


6 




1^2 




146 


7,520,000 


1733 


*' 




252 


39 




3 


6 




1>^2 


Water 


152 


6,646,000 


2242 


" 




253 


38 




4 


8 




1^2 




143 


4,560,000 


1282 


" 




291 


90 




— 


— 


M 





** 


136 


6,578,000 


5280 


" 


) Sudden 
3 Failure 


292 


90 




— 


— 







Air 


129 


3,940,000 


4580 




254 


38 




4 


8 




1/2 


*' 


139 


2,446,000 


617 


Excess 




255 


38 




4 


8 




1/2 




138 


2,247,000 


797 







CINDER CONCRETE. 



49 

50 
48 
152 
153 
154 
189 
190 
138 
139 
140 
163 
216 
217 
192 
193 
194 
218 



7 
7 
7 

30 
30 
30 
30 
30 
60 
60 
60 
30 
60 
60 
30 
30 
30 
30 



2 

2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
3 
3 
3 
3 
3 
3^ 



Water 
Air 

Water 
Air 



Water 
Air dry 

iv 

Water 
Air dry 

Air 

Water 
Ar 



120 
116 
111 
119 
112 
106 
109 
114 
114 
116 
119 
114 
107 
101 

107 
118 
106 



514,000 

876,000 

945,000 

1,358,000 

1,626,000 

1,399,000 

1,772,000 

1,021,000 

1,055,000 

1,783,000 

1,152,000 

1,168,000 

917,000 

916,000 

1,473,000 

1,447,000 

751,000 

533,000 



993 
1049 
976 
941 
705 
573 
847 
670 
682 
734 
544 
484 
511 
500 
405 



A— Atlas Cement ; M — Medusa Cement. 

It will be seen that the ultimate compressive resistance de- 
creases very uniformly as the percentage of materials other than 
cement in the mixture increases, and, also, that the modulus of 
elasticity increases with the ultimate resistance. The compress- 
ive resistance of the neat cement cubes is about 5,000 pounds per 



112 



COMPRESSIVE PROPERTIES, 



[Ch. VIv 



square inch and reduces to about i,ooo pounds for a 1:4:8 mix- 
ture. These compressive resistances have been plotted in the 
usual manner in Figure 6 and the results averaged by means of 



iSOO 



1000 



3200 



g 2400 



1600 



800 



^S^ 


.-^ 




































"V 


''>1 


^^ 


> 












No's 0: 
Lverag 


I Curve show 
eNo. o'f Tests 
















N 

2 


N 


^t?>c 


































'2 


s^ 


< 


•> 


s''. 
























c 




tS^c 


?^e 


3 




V. 


2 


\ 


'^, 


























>**• 


^'«« 








*%^ 


".^ 


*v 





1 2 3 1 5 6 7 8 9 10 11 12 13 U 15 16 17 18 
Parta of other Material to Cement 

FIG. 6.— FROM HENRY'S TESTS. 

a straight line, which may be expressed algebraically by the fol- 
lowing equation: 

^=4350— 258J (i) 

For Eq. (i), then, it will be seen that a neat cement mixture 



1100 

1000 
















































































" 


B 900 

?800 
a 
o3 700 


































,- 




^j, *•, 
















t 














, .<• ** 


• "* 






















^\ 


/ 






^^ 


.^ 


^ 












, 


,-- 


-- 


5 600 
1 

Isoo 

03 

v 

•|ioo 
a, 300 












5-/ 




^^ 




f-"*^ 








^ 


--- 


, — " 




















/ 


y: 


y 


/ 


/ 


^ ^ 


-' 


,^»» 


— 





- 
















jS 


v/ 


V 


/ 


.y 


^ 


^ 


'^ 






























¥y 


-^ 


^ 


























^200 

100 









/ 


} 


U 


¥ 
































/ 


f 
/ 


/ 


/ 


































/ 


/ 


/ 

































.0001 .0001 .001 

Proportionate Deformation 

FIG. 7.-FROM HENBY'S TESTS. 



.0018 



Art. 21.] COEFFICIENT OF ELASTICITY AND RESISTANCE. 1 1 3 

will have an ultimate resistance of 4,350 pounds, and that a mor- 
tar of I cement to 16J parts of other materials will have no 
strength at all. 

Table VI. also furnishes results of ultimate compressive re- 
sistances and coefficients of elasticity for the cinder specimens, 
and the results of these tests are also plotted in Figure 6; but it 
has not been thought proper to express these results by means 
of an equation. 

Figure 7 shows some stress-strain curves of compression tests 
made on the cinder concrete. In this case the elastic limit might 
be considered to be one-half of the ultimate resistance. 

From an examination of the coefficients of elasticity deter- 
mined by Henby it is impossible to check Bach's proposition 
that there is some mixture which attains the highest value of 
the coefficient, and that mixtures either leaner or richer have de- 



TABLE VII. 



Brand of Cement 


Mixture 


Average Com- 
pressive Strength, 
Lbs. per Sq. In. 


Coefficient of Elasticity in Lbs. 
per Sq. In. Between Loads of 
100 and 600 Lbs. per Sq. In. 


Gcrmania Portland. 


1:1:3 
1:2:3 
1:2:4 
1:2:5 
1:3:6 
1:1:3 
1:2:5 
1:1:3 
1:2:5 


2001 
1634 
1325 
1084 
788 
2834 
1600 
2414 
1223 






1, n 




,4 n 




4i 44 




Alpha Portland. . . . 
Atlas " 


2,500,000 
1,279,000 
3,125,000 
1,138,000 



creasing values. In these experiments the value of the coeffi- 
cient decreases rather uniformly as the mixtures become more 
lean. 

Table VII. is taken from the Watertown Arsenal Report for 
1898, and shows results of tests made on cinder concretes for the 
Eastern Expanded Metal Company of Boston. In all 84 twelve- 
inch cubes of various ages, made with different brands of ce- 
ment, were tested. Only the results of the better known brands 
are here abstracted, and only those which reached the age of 
about three months. Each result shown is an average of three 
tests. The cinder used was in the condition in which it came 



114 



COMPRESSIVE PROPERTIES, 



[Ch. VI. 



from the furnace; it was not sifted, and only the larger clinkers 
were broken. 

In the same Watertown Arsenal Report for 1898 are also re- 
corded results of tests on 95 cubes and prisms which were manu- 
factured at the Arsenal. Only those specimens in which Alpha 
cement was used are shown in Table VIII., the mixtures being 
1:1:3. The sand was bank sand, the pebbles were from the Ar- 



TABLE VIII.— 12-INCH CUBES— 1:1:3 ALPHA CEMENT. 



Kind of Stone 



Trap yz Inch 

44 ■3/ 4 4 

n 

/Trap % Inch I Part 1 

\ " 2V2 " ....2 Parts] 

f " 2>^ " ....I Part 
\ '♦ I " ....I " 

\ " 'A " ••'■I " 
Pebbles Yz Inch 

f Trap lYz Inch. ... 2 Parts \ 
\ Gravel y% Inch. . . I Part J 

Pebbles I>i Inch 

/ Pebbles ^ " . • I Part \ 
\ " Xyi " ..1 Parts/ 
Gravel y% Inch. ... I Part ] 

" Yz " ....I " \ 

Pebbles I^ Inch.. I " J 

Trap ^Yz Inch 

Trap 2V2 Inch I Part] 

Pebbles ^ Inch. ..I " \ 
Gravel Yi Inch. ..I " J 

Mixture 1:3:6 of I In. Trap. . 

Pebbles \Yz In. to 3 In 

Trap lYz Inch 

1:1 Mortar 

Neat Alpha Cement 



Ultimate C 
Resistance 
SQ: In. at 


ompressive 
in Lbs. per 
Age of— 


Coefficient of Elasticity in 

Lbs. per Sq. In. Bet Loads of 

100 and 600 Lbs. per Sq. In. 

at Age of— 


About 
1 Month 


About 
2 Months 


About 
1 Month 


About 
2 Months 


2800 
3200 
4917 


5021 
5272 


3,571,000 
8,333.000 
6,250,000 


4,167,000 


8,333,000 


4349 


4544 


8,333,000 


6,250,000 


4800 


5542* 


8,333,000 


8,333,000 


2992 


3870 


4,167,000 


3,125,000 


5024 


4700 


6,250,000 


12,500,000 


3817 


4018 


4,167.000 


2,778,000 


3800 


3490 


4,167,000 


5,000,000 


3000 


3800 


3,125,000 


3,125,000 


4140 


4523 


5,000,000 


12,500,000 


2700 




4,167,000 






2190 
3800 
3572 
4400 
5551* 


4800 


3,125,000 
4,062,000 
5,208,000 
5,000,000 
5,000,000 








6,250,000 








*Not 


fractured. 



senal grounds and the rock was broken trap of different sizes 
from Waltham, Mass. The f inch stone all passed a | inch sieve 
and was all retained on the next smaller size, viz., \ inch. The 
other graded sizes were obtained in a similar manner. The ages 
of the specimens varied from 7 to 76 days ; only those having an 



Art. 2 1 . ] COEFFICIENT OF ELASTICITY AND RESISTANCE. 



115 



age of 30 to 70 days need be discussed, since the others are of no 
practical importance. As shown, the results are for one speci- 



TABLE IX. 



Brand of Cement 



Genesee 



Wayland 



Ironclad 



Empire 



Champion. 



Approximate Composition 
by Parts 



Cement 



Sand 



Stone 



5 

7 

9 
12 
15 
16 

4 

6 

8 
II 

5 
7 

9J^ 
I2>^ 
13 

8 
II 
12 

10 
15 

6>^ 

8>^ 
II 

7 
10 
13 

6>^ 

8 
I0>^ 

7 
9 
4 

VA 

8 



Modulus of Elasticity in Lbs. 

per Sq. In. Between Loads 

per Sq. In. of 



100-600 



2,428,000 
2,619,000 
2,108,000 
1,403,000 
1,370,000 
1,087,000 
1,628,000 
2,263,000 
1,745,000 
1,801,000 
1,822,000 
2,314,000 
2,018,000 
1,528,000 
1,427,000 
3,072,000 
2,285,000 
1,845,000 
1,449,000 
1,318,000 
2,518,000 
1,752,000 
1,408,000 
3,273,000 
2,168,000 
1,792,000 
2,874,000 
2,292,000 
1,608,000 
2,685,000 
2,609,000 
2,081,000 
2,781,000 
2,609,000 
1,528,000 
2,780,000 
2,516,000 
1,602,000 



100-1000 



2,113,000 
2,748,000 
1,974,000 
1,382,000 
1,300,000 



1,508,000 
2,081,000 
1,580,000 
1,499,000 
1,749,000 
2,002,000 
1,721,000 
1,432,000 
1,273,000 
2,265,000 
1,991,000 
1,555,000 
1,218,000 
1,100,000 
2,295,000 
1,227,000 



2,937,000 
1,757,000 
1,468,000 
2,505,000 
1,890,000 
1,266,000 
2,446,000 
2,176,000 
1,622,000 
2,253,000 
2,207,000 
1,046,000 
2,571,000 
2,228,000 



CO ♦i-ua a 
a.tOi-J"- 

U 4> E cr 
^ c c « 



4080 
3291 
2930 
2226 
1842 
1365 
3330 
2519 
2567 
2094 
4165 
3221 
23II 
I85I 
I7I3 
4031 
3465 
2230 
1843 
1723 
2852 
1927 
1665 
3678 
2296 
1880 
3521 
246O 
1774 
3579 
2545 
1899 
2928 
2459 
1495 
3127 
2377 
1393 



men only. It will be seen that the values of the coefficient of 
elasticity are very high. This may be explained by the density 
of the specimens, which averaged about 150 pounds per cubic 



116 



COMPRESSIVE PROPERTIES, 



[Ch. VL 



foot; whereas, in the tests made by Rafter, and to be noted later, 
the average weight was only about 140 pounds per cubic foot. 

Table IX. is taken 
from the Watertown 
Arsenal Report for 
1898 and records ex- 
periments made for 
Mr. George W. Rafter 
on twelve-inch cubes 
ol concrete made with 
various brands of ce- 
ment. Mr. Rafter's 
tests are explained in 
greater detail on 
page 121 et seq. ; here 
are only given the experiments concerning the elasticity. The 
average age of the specimens was about one year, seven and 
B 20001 — \ — \ — I — I — \ — I — I ^,^-— *' — \ — \ — \ — \ — 1 I , -T one-half months. 



5000 










^ 


^ 














Broke at 482 olj^^ 








y 


^' 














^ 




^>- 










? 




/¥ 










^ 


1? 


ar 














P. 

in 


f 


r- 








/ 


/- 


\ 




















1 


I 








/# 
























1 


I 








..^" 

y 


























0) 


\ 




A 




























3> 




/ 






)(^ 


4: 


8 Cohcrete^^ 




X 


^^^ 


oue- 


at-U95JDS._ 


1 


/ 




^ 


^ 




Tot 


a\E 


on?: 


itious 




b 





f 


1 


1 































.001 .Ovo .01 .015 

Deformations in Gauged Length in Inches. 
FIG. 8. 



.017 



02 C 

,: " 1000 



as 

a 
6 











J 


^ 


.#-" 


^ 




-»^ 


: — 


— 


■-f'^^^^f^^^ 




y 


X 


i--^ 




(— 




if— 




Ali)ha Port 
1 Cement 


and Cei 


leiit 


Cou 


•■reti 




/ 


X 


^ 














3£ 

6 


and! 

jVlTra 


) Rock 










/ 










j 






12|lDcHCube i Ye 
Gauge Lengtli = 5 Ii 


irOld 

.s. 1 







.001 



.003 .01 .015 

Deformations in Gauged Length in Inches. 
FIG. 9. 



.018 



The majority of 
results are aver- 
ages of tests 
made on two to 
four specimens ; 
n o distinction 
has been drawn between dry, plastic or excess. The gauged 
length on which the elastic properties were measured was five 
inches. The experi- 
ments are tabulated in 
the order of the richness 
of the various mixtures. 
It will be seen, in 
general, that the values 
of the modulus of elas- 
ticity decrease with the 
leanness of the mixture, 

ine Ultimate CrUSnmg Deformations m Gauged Length in.lnches, 

resistance also decreases fig. lo. 



u 3000 

D 
P. 

g 2000 

u 
■<-> 

CQ 

Q 1000 

> 



































r^ 


-/ 


X 






^ 


r 


r 


^r- 


iSr 


)ke- 


it.3. 


89-1 


)S._ 


) 


/ 




/ 


A 


\X 


A 


pha 


For 


tlau 


I Cemen 


tCo 


ncre 


te 


1 






'? 






















4 


/ 








2 Sand 














t 


J 










- ^■V%-'{-T\j.Y rMzsr 










1 


/ 










12 Inch Cube 1 Vear 


Old 






V 





















Art. 21.] COEFFICIENT OF ELASTICITY AND RESISTANCE. 



I 17 



























-- 








— 1 




i i 












-- 


iOOO 






































1 






















1 

1 










































y .,. 


^B: 


■oke at 3369 Lbs. 

i 1 1 1 




































3000 




/y 





Composition: 
Wayland Cement 1 ) 

SnnH 1 V 














Broke at 


2881 Lbs. 






2000 


A A ! 










^^ 




•X 














' 




Broken Stone 6.43) 






} 





^ 






Ironclad Cement 1 \ 






1000 


i/\ 


f 






Age, 1 Year, 3 Mos.. 20 Days 




h 


/ 








Sand 1 [• 
Broken Stone 7.76) 










12 "i Cube 


















if 








Age, 1 Year. 7 Mos., 15 Days 


— 




1 


























' 


12' 


Cu 


be 




















































































































Broke 


at 4:198 |Lbs 






4000 








Wayland Cement 1 \ 
Sand 3 [ 
Broken Stone 8.29-- 














/ 




X 


^' 














3000 




















/ 




/" 


























Aj 


re, 1 Year, 8 Mos., 17 D 


lys 










' 


/ 








































[ 
Broke at 


223C 


Lbs. 


/ 


/ 


f 






Empire Cement 1 ) 
Sand 2 [• 
Broken Stone 7.5 ) 






2000 










>* 


p: 


*— 




-* ■ 












/ 


/ 












1000 




A 


^ 
























U 








Ag 


'e, 1 Year, 8 Mos., 14 Days 




A 


r 










12" 


Cul 


)e 












If 




12" 


Cu 


)e 




















7 




























f 


















































































4000 
























































J 


& 


y 


^B 


rok 


eat 


389 


7 Lbs. 






















Mortar 

Empire Cement I \ 

Sand 4> 






3000 


/ 


J 


/ 




































/ 


1 










Mortar 

Empire Cement 1 ) 

Sand zi 














Ag 


e, 1 Year, 7'Mos., 22 Da 


ys 




2000 


■. 


f 








































i 










Ai 


fe, 1 Year, 7 Mos., 18 Di 


lys 






V 




.f< 


— 


Br< 


)ke 


at 1717 


.lbs. 








1000 


I 




























/ 




y 
























12' 


Cu 


je 




















f/ 


r 






12' 


1 
Cube 
















1 




























f 




















































^ 






y 


Br( 


)ke 


It 


















4000 






Moi-tar 








/ 






/ 


/ 


4763 Lt)S. 

1 1 






















El 


npire Cement 1 ) 
nd Z) 








{ 




/ 


/ 


1 
i 






















3000 




Age, 1 


Year, T Mos., 18 Days 




/ 




> 


/ 


1 

1 1 
















1 










Brpke 


1 
at 2494 ,Lbs 






/ 




/ 




Mortar Prism 






1- 




Broke at 2755 1 

^111 


jbs. 


2000 


J 


k" 


X 


.X 












/ 


/ 


t 


A 


pha Cement 1 ) 






/ 


Mortar Prism 

6"x6"xl8" 
Aere, 38 Days 




/ 


/ 


















/ 


/ 




Fme aana i > 

Age, 36 Days 

1 Day in Mold > 

35 Days in Water ) 

Gauged L,engtli 10 " 




/ 




1000 


{/ 












1 






> 


K 






/ 


^7 1 


1 Day in Mold ] 


1 




12' 


Cube 

1 












/ 










Gaugeu Length lO " 




^ 




















r 








1 ' ' 1 

1 : 1 1 



















.01 



.02 



.03 .04 .01 .02 .0.3 .04 

Deformations in Gauged Length of 5 Inches. 



.01 .02 



.0.3 



.04 



FIG. 11. 



118 



COMPRESSIVE PROPERTIES. 



[Ch. VI. 



with the leanness of the mixture; in other worr's, the modulus of 
elasticity is some function of the ultimate crushing resistance. 

Table IX. also shows that the modulus is not a constant quan- 
tity for any one specimen. The values given are calculated be- 
tween two increments of stress, from lOO to 600 pounds and from 
100 to 1,000 pounds per square inch. In every instance the val- 
ues for the second increment of stress are smaller. 

Figures 8 to 12 are all abstracted from the Watertown Ar- 
senal Report for 1898 and 1901, and show clearly the elastic be- 
havior of some of the mixtures which have been tabulated on the 



bOOO 
















r 




r 


r 


~ 




r 


r 


^ 


«-- 


r 




r 






- 


^^-T-^ 






f*" 








2000 






















-Jr 


^ 


Xf 








-»» 







-r- 




-*- 


1 




























jr^ 


-H^ 


1 




-#■ 




— 


*—■ 


■"^ 












Specimen same as below 
Age,l Year, 6 Mos., 25 Das 
n Mold, 23 Hours 








1000 






^ 


^ 






,-tr^ 


























/■Seti 


. I 


— 


} 


6 


^ 


.*- 


■^ 
































( 1.1 Air, 27 Das, / 




>■ 




































































































































1000 


















































































,v>' 


.ol^^ 




^ 


>- 


^ 








if 


Tf 


tal 


S)^g^ 


Oil 




*- 


-" 














3000 














?U 


^ 


,-^ 












^ 




jt- 


H 


-1 
































i 


y 


^ 










1^ 


^ 




-ir 


— -ji 


Genesee Cenient\ 
























2000 






^ 


y 








^ 


^ 


-<*-' 












4.71 Broken, stone ) 




lan 


« \^ 


T\(I 


>1.4 


09 


V.nii 












/ 






^ 


^ 
















Cons 

Age, 1 

Wt, IK 


?la?9 tS:;' S^s J? W^^^i'M^^^^^^^^^^ 


)as. 


— 


1000 


i 




/" 


^ 




















>rCu.Ft.= 147.16 lbs 

Specimen 12" Cube - 
Gauge Length =• 5 Ins. 


1 In Band, 1 I'ear, 1 JM0.,1U Das. 
\In Air, 3 Mos., 7 Das. 


/ 


1 
















































Y 






























1 


1 

























.001 .005 .01 .015 .02 

Deformatlou in Gauged Length in Inches 

FIG. 12. 



.025 



.028 



preceding pages. Two curves are shown, the one to the right 
being the curve of total deformation and the other the curve of 
sets. The curves are characteristic of all the tests made, and in- 
spection tends to confirm the opinion that concrete mixtures in 
compression have a point which might be called the elastic limit, 
at about 5-10 or 6-10 of the ultimate crushing resistance. In the 
case of the neat cements or mortars, this elastic limit approaches 
more closely to the ultimate resistance, having a value of perhaps 
8-10 of it. 

Professor E. J. McCaustland records in the Transactions of 



Art. 21.] COEFFICIENT OF ELASTICITY AND RESISTANCE, 



119 



the American Society of Civil Engineers, 1903, some experi- 
ments which he made on concrete and mortar columns of various 
compositions and of various ages, and for which he determined 
the true coefficient of elasticity at 500 pounds per square inch. 

Table X. shows the results of his tests on these columns, which 
were circular, 10 inches in diameter and 40 inches long. It will 
be seen that the coefficients varied, although not uniformly, with 
the variation in the ultimate compressive resistance, and, from 
the stress-strain curves which are shown in the original paper, the 
material might be said to have an elastic limit of 5-10 to 6-10 of 
the ultimate resistance. 









TABLE 


X. 






Proportions 


Age in 


Coefficient of 

Elasticity in 

Lbs. per Sq. In. 


Ultimate Crushing 

Strength 

Lbs. per Sq. In. 


Cement 


Sand 


Broken Stone 


Months 




2 


3 


14 


1,050,000 


1000 '1 




2 


3 


II 


1,530,000 


1752 I ,^.,, 




2 


3 


13 


3,060,000 


I215 
2650 , 


' iv-Vt 




2 


3 


14 


2,010,000 






3 


4 


10 


1,100,000 


1484 1 






3 


4 


ir 


1,380,000 


1382 


> I4II 




3 


4 


14 


1,425,000 


1230 




3 


4 


II 


- 1,441,000 


1550 . 






3 


5 


14 


1.450,000 


1550 1 






3 
3 


5 . 
5 


14 
14 


1,531,000 


1500 
1792 

1 170 j 


> 1504 




3 


5 


14 


1,050,000 






2 


5 


15 


840,000 


1045 ' 




2 


5 


15 


1,510,000 


^^55 i 1532 
1450 ^ ^^^^ 

1680 




2 


5 


14 


1,372,500 




2 


5 


23 






4 


— 


23 


2,775,000 


2660 




2 


— 


23 


4,625,000 


3410 




3 


— 


23 


3,700,000 


2250 



Figure 13 presents the results of compressive experiments re- 
ported by Professor Edgar Marburg to the American Society 
for Testing Materials, at its annual meeting, 1904. These stress- 
strain diagrams represent tests on four 6x6-inch prisms, 24 inches 
long; the deformations were measured on a gauge length of 18.5 
inches. The concrete was composed of i part of Delaware River 
bar sand, to 2 parts of Atlas Portland Cement, to 4 parts of f-inch 
broken trap rock; the materials were mixed rather wet. The age 



120 



COMPRESSIVE PROPERTIES. 



[Ch. VI. 



of the specimens, all being stored in air, was 30 days, and the 
average weight 154 pounds per cubic foot. 



.1200 r 




~ 


—- 




— 


"TT 




TTT 




- 




•T-rrr 


1 


- 


~ 


- 


— 






— p- 






- 


r 




— r-| 


,^-r'' II 1 i-t^' 1 i ! 


, 1 


' i ' 






































1 


























1 


-H 1 ! 


! |.«^l 


1 ! ' 




1 


1 1 






































1 








1 
















>i 


r^ 


1 ' i 


^^ 


J ! 




1 


1 •■ 












































1 


- 


- 








1 






^"^ 


,^ 




1 


1 V 


' 








i 


1 


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f-^ 


* 


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M-r 




, ? 








Ir^'^ 




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I 


\ 




































1 














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"+" 1 






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r'C 










r 




1 






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1 














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j ■ 
























^^ 


















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j 




^ 




















./ 


















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\ 


1 














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' 
















j 


' ' 






















^ 


■ 






























/ 






V 






1 


1 














1 




















^ 














./ 


1 








1 






'/ 








} 






i 


















1 


1 : ; 


• 














y 










1 










' 


1 






/ 


1 






^^ 


























1 1 ' 


i/i 












r 














. 






1 








1 






1 1 




/ 








1 


















1 


1 ' ' 












i/l 














\ 




1 


1 


1 1 


; 








1 1 


































Mil 


(U 










JlU- 












^ 






IL~r 




1 


/ 






'T 




r 








: 


















1 


1 ; 












/ 




















1 : 


1 1 


. 


.r 












1 






•d 








, 










! 


i 








1.1! 




1 1 ' j 


4/ 








Specimens 6x6 Length 24" ~.l 
Deformation measured between [- 
Collars, screwed to Specimen 
Gage Length 18" f 


^ 




















t 








' ' ' li 


1 




I 


. i.^i 


1 






§ 








y 


1 1 






1' 




1 








III/ 






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t\ 
















/ 




1 i 






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1 , / 


1 




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1 








1 




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^ ' ■ 


iM 1 






1 1 












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1 


1 1 1 1 


1 ^ 1 1 


J 1 1 


1 


1 






t 












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I 








1 1 


1 |.' ' 






1 ; 1 




-_- 








1 1 


1 ;■ ! 1 




1 






1 1 




I'M 


■/I 1 ' 


MM 


, 








1 1 


1 






1 


_^L_L 












/ 1 ! 




1 






1 1 i 


1 •' 


i 1 ' 


r ! ' ; . 1 1 1 






















1 




200 " 








i 1 1 


-' 1 i 1 


1 1 




■ 1 1 






1 


1 1 




1 




















i ! 1 


1 ' i ' 








I A 1 


•J 


1 1 


III 


1 1 ■ 


]■ II i 


1 


1 


ji 1 
























1 




1 ■ ' 




tiiti: 


1 1 j 


; 


1 1 






,1111 




1 




1 


















1 




1 


1 


-Li :X 




^4 ■ 




/I 


1 1 


i 1 i 


ill 


-'III! 


' 1 


'"J-IE 
























1 











' ' 1 i 


•1 1 ' 


II 


1 1 


/ , ; i i 


■III" 




.' i . 


1 










1 




■ MM 


: 1 1 r 



Ot'OOOO 0."0005 o."ooio O."0000 0."0005 

0:00 0."0005 o."oooo 

Compression per inoli length 



0.0005 



0.0010 



FIG. 13.— MARBURG'S TESTS. 

The figure shows the stress-strain curve to be sensibly a 
straight line to a point about one-half the ultimate resistance. 

The values of the compressive coefficient of elasticity, calcu- 
lated without reference to any permanent set occurring in con- 
nection with the applied stresses, are given in the following table; 
the specimens in the figure are numbered from left to right: 







TABLE XI. 




Specimen 
No. 


Ultimate Compressive 

Resistance 

in Lbs. per Sq. In. 


Coefficient of 

Elasticity 

in Lbs. per Sq. In. 


Determined for 
Stresses of— 


I 


II66 
II54 
1277 
I3I6 


2,000,000 
2,000,000 
2,300,000 
2,700,000 


0—^00 Lbs. per Sq. \rx. 
— 500 


2 


3 

4 


0—500 
0—600 



It is seen that the coefficient increases with the ultimate re- 
sistance. 

Professor Marburg also furnishes the average ultimate com- 
pressive resistance of nineteen 6-inch cubes of the same materials 
and same age, but taken from batches mixed at various times. 
The value given is 1643 pounds per square inch. Two specimens, 





Enlarged Views of Figures Opposite Page 86. 
The Location of the Points of Fracture, as Well as Details of the Extensometer, Are Clearly Shown. 



Art 22.] ULTIMATE COMPRESSIVE RESISTANCE. 1 2 1 

mixed with less water and thoroughly rammed, developed resist- 
ances, however, greater than the 100,000-pound capacity of the 
machine used. 

Art. 22. - Ultimate Compressive Resistance. 

George W. Rafter has recorded in the Report of the State 
Engineer of New York for 1897 results of compression tests 
made on 544 twelve-inch cubes whose age at the time of testing 
averaged about 600 days. The concrete was prepared in three 
different ways — in dry blocks, in which the mortar was only a 
little more moist than damp earth; in plastic blocks, in which 
the mortar was like that used by masons; and in blocks, in which 
the water was in excess, so that the concrete quaked like liver 
under moderate ramming. From every batch mixed in one of 
these ways four specimens were prepared and stored differently. 
One block was placed in water from the time of making (sum- 
mer of 1896) until December i, 1896, then buried in sand until 
January 10, 1898, when it was shipped from the place of manu- 
facture to the Watertown Arsenal in Massachusetts. The sec- 
ond block stood in a cool cellar until shipment; the third block 
was exposed to the weather, and the fourth block was covered 
with burlap and was wet with water several times a day until 
November i, 1896, after which it took the weather as it came 
until the day of shipment. The tests were made with Portland 
cement only. The sand was hand-broken Portage sandstone 
passing through a two-inch ring. 

Examination of these detailed experiments shows that the four 
specimens of any one series treated to the various conditions of 
weather gave rather uniform results; at least, it cannot be no- 
ticed that any one condition shows radically worse effects than 
any other. In further considering these experiments, therefore, 
the average of the four specimens prepared at any one time will 
be used. 

Mr. Rafter does not express the ingredients of a concrete mix- 
ture in the usual way, such as one part of cement to three of 
sand, to three of stone, either by weight or measure; but he ex- 
presses the relations, in percentages, between a definite mortar, 



122 



COMPRESSIVE PROPERTIES. 



[Ch. VI. 



say, 1 :3, to a unit weight of stone. In order to make his results 
comparable to others the following table has been prepared, 
which expresses roughly Mr. Rafter's nomenclature in the more 



Percentage of Mortar 


Ratio of Cement to Sand in tlie Mortar 


1:1 


1:2 


1:3 


1:4 


1:5 


1:6 


33 


1:1:5 
1:1:4 


1:2:7 
1:2:6 


1:3:9^ 
1:3:8 


1:4:12 
1:4:10}^ 


1:5:15 
1:5:12 


I:6:I6>^ 


40 







usual terms. Two percentages of mortar to stone were used, 33 
per cent, and 40 per cent., and six different mortars, varying 
from I :i to 1 :6. 

TABLE I. 



Consistency of Mortar 



Parts of 
Cement to Sand 



Percentage of 
Mortar to Stone 



Ultimate Crushing Strength 

in Lbs. per Sq. In. 

Average of 4 Specimens 



Excess of Water. 



Dry. 



Plastic 



Excess of Water. 



Dry. 



Plastic. 



33% 



40 



fo 



3764 
2847 
1723 
1767 
I44I 
4267 
2888 
2056 
I8I0 
1537 
4072 
2777 
2207 
1600 
1586 
3256 
3168 
2016 
1670 
1400 
3966 
3404 
2179 
I67I 
1559 
4123 
2960 
2027 
1750 
1465 



It will be seen, for instance, that the concrete known as i ;3 
mortar, 40 per cent, may be expressed as a i :3 :8 concrete. 



Art. 22.] 



ULTIMATE COMPRESSIVE RESISTANCE, 



123 



Table I. is characteristic and shows the results obtained for 
Wayland Portland cements only, being the tests numbered 29 
to 58 in the Report. The results obtained from the other brands 
of cements will be discussed, but need not be given here in de- 
tail, since they show but little variation. 

In the Transactions of the American Society of Civil Engi- 
neers, December, 1899, Professor I. O. Baker has tabulated and 
arranged very concisely all of Mr. Rafter's experiments, and the 
following tables are taken from his discussion of the experiments : 

TABLE II. 





Amount of Mortar 


Strength of the 40% 

Concrete in Terms of That 

of the 33% 


Plasticity of Mortar 


33% 


40% 




Crushing Strengtli in Lbs. per Sq. In. 


Drv 


2408 
2259 
2133 


2332 
2329 
2227 


105% 


•^^y 

Plastic 


103% 




104% 






2267 


2363 


104% 





It will be seen, therefore, that the effect of plasticity is not of 
great importance; in practice, what little gain in strength the 
dry mixed specimens may show is negligible in the face of other 
considerations, the principal one being the increased cost of 



TABLE III. 





Amount of Mortar 


Strength of the 40% 

Concrete in Terms of That 

of the 33% 


Proportions in the Mortar 


33% 


40% 




Crushing Strength in Lbs. per Sq. In. 


I Cement: 2 Sand 

I Cement: 3 Sand 

I Cement: 4 Sand 


2640 
1893 
1684 


2820 
1905 
1689 


107% 
102% 
100% 



manufacture of dry over the wet concretes. This is due to the 
extra cost of the ramming required. 

Table III. shows that there is but very little increase in strength 
of the 40 per cent, concretes as compared to the 33 per cent. 
This may possibly be explained by the fact that in the 33 per cent, 
specimens the mortar did not entirely fill the voids in the stone; 
the stones therefore had direct bearing on each other, while in the 



124 



COMPRESSIVE PROPERTIES, 



[Ch. VI. 



40 per cent, concrete the voids were just about filled; the strength 
of the mortar itself in that case had less influence than the direct 
bearing of the stones on each other in the first instance. 

Mr. Rafter's method of determining the proportions of the in- 
gredients in the mixture is open to criticism. The densest con- 
crete is formed when the sand grains fill as many voids as pos- 
sible in the stone, and the cement grains then fill as many as 
possible of the remaining voids in the stone-sand mixture. This 
is different from first filling the voids in the sand with cement 
and then the voids in the stone with mortar. In the latter case 



TABLE IV. 



Brand of Cement 



Cement 


to Sand 


by Measure 




I 




2 




3 




4 




6 




I 




2 




I 




2 




3 




4 




5 




6 




2 



Percentage of 

Mixed Mortar to 

Broken Stone 



Ultimate Crushing 

Strength in 

Lbs. per Sq. In. 



Wayland Portland 



Saylor's Natural 



33% 

42% 
42% 
42% 
33% 



42% 
42% 
42% 
42% 
42% 
42% 



3154 
2454 
1720 
1363 
I43I 
4381 
2409 
2978 
1890 
1542 
II32 
1087 
729 
2550 



the voids in the sand will usually be found to be greater than the 
sum of the voids in the stone-sand mixture. 

Table IV. is taken from the Report of the State Engineer of 
New York for 1894, and records experiments which were made 
by Mr. George W. Rafter previous to those just tabulated. These 
tests were made on 174 concrete cubes of one cubic foot each 
whose average age was three months. The stone which was 
used was hard quarry stone, broken to pass a two-inch ring and 
was washed clean. Each result shown is an average obtained 
from two to six specimens. Some of the blocks were placed in 
water after the final set had taken place. The result obtained 
from such blocks was averaged in with others in the table, it 
being found almost uniformly, however, that the ones which 



Art. 22.] 



ULTIMATE COMPRESSIVE RESISTANCE. 



125 



hardened in water, as compared to those which set in air, were 
very sHghtly stronger. In these experiments Mr. Rafter also 
expressed the ratios between the materials by a relation between 
the broken stone and the mixed mortar, having in mind that the 
mortar should more than fill, the voids in the stone; this explains 
column three of the table. 

Table V. is taken from the Watertown Arsenal Report for 

TABLE V. 



Composition 


Ult. Strength in 


Lbs. per Sq. In. 


at the Age of 


Cement 


Sand 


Gravel 


Stone 


30 Days 


7 Months 


1 Year 




IK 


— 


4 


1448 


2213 


2917 




3 


— 


7% 


1024 


1987 


2076 




2 


3 


4 


1096 


2180 


2094 




2 


7 


— 


746 


1633 


1792 




2X 


8 


— 


739 


1540 


1448 



1901, and shows the ultimate compressive resistance, at various 
ages, of 12-inch concrete cubes made from one brand of cement. 
Each result shown is an average of three tests. It will be seen 
that this concrete did not gain in strength after seven months. 

Tables VI. and VII. are taken from the same Report; the for- 
mer shows the ultimate crushing strength of concrete prismis 

TABLE VL 



Composition 


Number 

of 

Specimens 

Tested 


Ultimate Crushing 
Strength 


Cement 


Sand 


Stone 


in Lbs. per Sq. In. 


I 

I 
I 


2^ 


J4— >^ In. to 2 In. Diam. 1 
1 Pebbles / 
r A—% In. to 2>^ In. Diam. 1 
\ Gravel J 
f 4— I In. to ^Yz In. Diam. \ 
\ Hard Trap Rock J 


8 
6 
6 


2326 
3363 
3886 



6x6x36 inches in length, pressed on their ends, the average age 
being about 33 days. The results show that the same ratio of 
cement to aggregate, but with different sizes of stone, may fur- 
nish entirely different balancing of the mixture, and may thus 
affect directly the ultimate crushing strength. 

Table VII. shows the ultimate crushing resistance of 2-inch 



126 



COMPRESSIVE PROPERTIES. 



[Ch. VI. 



cubes made of various brands of neat cement tested at various 
ages. Each value is a mean of from five to six specimens, all of 
which set and hardened in the air. 

The following series of compression tests (Table VIII.) on 
cement and mortar bricks, 9 inches x 4J inches x 3 inches, is re- 

TABLE VII. 



Age 


Ultimate Compressive Strength in Lbs. per Sq. In. 


in 
Days 


Storm King 
Portland 


Alsen 
Portland 


Lehigh 
Portland 


Hoffman 
Rosendale 


Norton 
Rosendale 


Potomac 
Rosendale 


I 

7 

14.... 

30.... 


577 
1400 
1820 
2160 


1 140 
3980 
3830 
4170 




261 

543 

676 

lOIO 


225 
476 
609 
878 


145 

403 

590 

lOIO 


4540 
5210 
5760 



corded by John Grant in the Proceedings of the Institution of 
Civil Engineers, Vol. XXXII. , page 288. Ten specimens were 
prepared from each mixture, the composition being as shown in 
the table; five were allowed to harden in air and five in water, 
the age when tested being one year. The results as published 
are expressed in tons, and in reducing the figures it was assumed 

TABLE VIII. 



Mixture 


Crushing Resistance in Lbs. per Sq. In. 


Left in- 


Cement : Sand 


Air 


Water 


Neat 


5370 
4580 
3880 
2980 
2420 
2070 
1680 
1600 
1070 
970 
855 


7350 
4620 


I'l 


1-2 


3170 


1:3 


1470 


1:4 


II 60 


1:5 

1:6 


635 
622 


1:7 


584 
453 
412 
312 


I«8 


I.Q 


PIO 





that the ton of 2,240 pounds was meant. The specimens were 
either rammed or pressed by hydraulic press at the time of 
making. 

Grant also made a series of tests (Table IX.) on concrete 
blocks, some of which set in air and were so kept for one year, 



Art. 22.] 



ULTIMATE COMPRESSIVE RESISTANCE. 



127 



and some of which set and were kept in water for the same period 
of time. The blocks were either 12 or 6 inch cubes, but only 

TABLE IX. 





12-Inch Cubes 


6-Inch Cubes 


Proportions of 
Cement to Sand 


Crushing Resistance in Lbs. per Sq. In. 




Kept in Air 


Kept in Water 


Kept in Air 


Kept in Water 


i-i 




2660 
2490 
1800 
1690 
1550 
1420 
1250 
II80 
1060 
745 


2360 

2680 

1870 

1870 

1520 

1270 

1030 

840 

750 

625 


2080 


1:2 

1:3 


2320 

1760 

1600 

1380 

1250 

1 160 

950 

840 

760 


2150 
2210 


I '4 


1740 


I '5 


2210 


1:6 

1-7 


1220 
990 
840 
680 


1-8 


I -9 


I'lO 


625 





those cubes in which the material was pressed or rammed in the 
moulds are here considered. 

It appears that each figure is the average of two tests, but the 

TABLE X. 



1 Composition 


Age 


Ult. Resist. 

in Lbs. 
per Sq. In. 




Cement 


Sand 


Broken Stone 


Years 


Months 


Alpha Portland .... 




2* 




J 


— 


4906 




" " .... 




2 


4 — Y% In. Trap 




— 


3187 


" " .... 




3 


6 




— 


2070 


4* 41 




4 


8 




— 


1499 


44 44 




5 


10 




— 


949 


44 41 




6 


12 




— 


791 


44 44 




2 


^\ Trap / 


2 


— 


2789 


44 44 




2 


4{'\^4'"-} 


2 


— 


2549 


44 44 




2 


4 — IYt. In. Trap 


2 


— 


2466 


44 44 




2 


7 




2 


24O6 


44 44 




2 


{\y^ to 3 In.1 
^ \ Pebbles / 




2 


3589 


44 44 




2 


^\ Brok'n Brick/ 




2 


3241 


44 44 




3 


6 




I 


2545 


44 tt 




4 






I 


1446 


.... 





*Granite dust. 



composition of the concrete is not clearly explained; the aggre- 
gate is called ballast and sand. The tables are inserted on ac- 



128 



COMPRESSIVE PROPERTIES, 



[Ch. VI. 



count of the interest attached to them, for the experiments were 
made in 1867. 

Table X. is taken from the Watertown Arsenal Report for the 



TABLE XI. 


Parts by Weight of Sand to Cement 


Ultimate Crushing Resistance per Sq. In. 


1:1 


II33O 


\:\y2 


10390 


1:2 


9520 


I:2>^ 


8II0 


1:3 


6I4O 


I:3>^ 


6280 


1:4 


5230 



year 1901, and shows the ultimate crushing resistance of 12 inch 
cubes, composed of various proportions of cement, sand and 



broken stone. 



TABLE XII. 



Brand of Cement 



Percentage 
of Water 


Compress 
Sq. 


ve Strength in Lbs. per 
[n. at an Age of — 


7 Days 


1 Month 


3 Months 


25 


6010 


7340 


8580 


25 


3490 


5370 


5870 


26.8 


4280 


5590 


6310 


18 


5780 


5990 


6980 


22;^ 


4620 


5I8O 


5930 


25 


5560 


5980 


7730 


30 


5030 


5620 


6810 


25 


5630 


6640 


7630 


29.2 


3510 


4940 


5510 


26.7 


2750 


4030 


4660 


26.7 


2II0 


2970 


3430 


18 


3860 


3970 


4490 


28;5^ 


1300 


1790 


2II0 


18 


3050 


3470 


4470 


33.4 


356 


1090 


1530 


38.7 


620 


II30 


1560 


36.2 


464 


790 


1230 


41.2 


566 


1020 


1420 


38.7 


407 


1090 


1440 


39.6 


472 


880 


1570 


35.8 


750 


1360 


2220 


39.2 


423 


840 


IIIO 



Alpha Portland 

Atlas " 

Lehigh " 

Star Portland 

44 4 4 

Whitehall Portland 

Alsen " 

Josson " 

Cathedral " 

Silica Cement 

Austin Natural 

Bonneville Improved Natural 

Hoffman Natural 

Mankato " 

Newark & Rosendale Natural 

Norton Natural 

Obelisk " 

Potomac " 



Table XL gives the values of the compressive resistance of ce- 
ment mortar cubes; the tests were made for the United States 
Engineering Corps and are recorded in the Watertown Arsenal 



Art. 22.] ULTIMATE COMPRESSIVE RESISTANCE. 129 

Report for 1902. The ciij^es were six-inch, of Atlas Portland 
cement, and the sand used was natural, 43.62 per cent, passing 
the No. 30 sieve. The cubes were each kept three months in dry 
air, fifteen days in water at 65 degrees Fahr., and then in air until 
the date of crushing, almost two and a half years after making. 
The compressed surfaces were faced with plaster of Paris. The 
rapid decrease in the ultimate crushing resistance as the per- 
centage of sand in the mixture increases is worthy of note. 
These tests are inserted on account of the extraordinary com- 
pressive strengths attained. The age of the specimens hardly 
accounts for this. Table XII., which is taken from the same re- 
port, shows the ultimate crushing strength of four-inch cubes 
of neat cement with various brands of Portland and natural 
cements. Each, result is a mean of from four to foe speci- 



TABLE : 


XIII. 






Ultimate Crushing Strength in 
Lbs. per Sq. In. 




With Fine Sand 


With Coarse, Sharp Sand 




1595 

II85 

985 


1825 
2145 
II02 


Selected Stone, Containing Some Mica. . 

^tnno ^ t>\oriO(\ fnr TI^f>. ............... 







mens. All the specimens set in air. In not one of these tests 
did the ultimate crushing resistance approach that shown in 
Table XL 

Table XIII. gives the crushing strength of concrete composed 
of one part Portland cement, three parts sand and five parts 
stone, in eight-inch cubes, as reported by T. S. Clark in Engi- 
neering News of July 24, 1902. The table is given for the pur- 
pose of showing that dififerent crushing strengths may be attained 
by concrete with different classes of stone. The cubes were kept 
in air twenty-four hours and in water five months before being 
tested. The three kinds of stone used were standard limestone, 
a stone containing a large amount of mica and which had been 
rejected for use, and a better quality of this rejected stone con- 
taining less mica. It will be seen that the quality of both the 
sand and the stone bears intimate relation to the final crushing 



130 



COMPRESSIVE PROPERTIES, 



[Ch. VI. 



strength, and the rather vague opinion that a calcareous stone is 
better than other kinds is to a certain extent corroborated. 

Setting Under Water — Table XIV. is taken from the Report 
of the Watertown Arsenal for 1902, and furnishes comparative 
crushing tests on mortars which were allowed to set both in air 
and in water. The majority of the specimens were two-inch 
cubes; larger size cubes are noted. The specimens which were 
placed in water were allowed to set first one day in air, and each 
result is an average of from four to five specimens. It will be 
seen that almost uniformly those specimens which set under 
water attained the greater compressive strength. The table only 
shows results for one brand of cement, but in all seven brands 

TABLE XIV. 



Brand of Cement 



Composition 


Age in 


Days 


Compress- 
ive Strength 










Cement 


Sand 


Water 
Per Ct. 


Air 


Water 


in Lbs. 
per Sq. In. 






32.0 


7 


— 


2540 






32.0 


I 


6 


2580 






32.0 


30 


— 


3010 






32.0 


I 


29 


3470 






32.0 


92 


— 


3390 






32.0 


I 


91 


4550 






32.0 


93 


— 


4100 






32.0 


I 


92 


6590 






33.7 


92 


— 


3555 






33.7 


I 


91 


5000 






33.7 


92 


— 


3805 






33.7 


I 


91 


5630 






32.0 


183 


— 


3370 






32.0 


I 


182 


4800 



Remarks 



Atlas. 



3 In. Cubes 1 

3 In. Cubes 

4 In. Cubes I 
4 In. Cubes | 
6 In. Cubes I 
6 In. Cubes j 



tn 






were tested, for neat, i:i and 1:3 mixtures. All the tests furnish 
similar results. 

These results do not corroborate those of Grant, previously 
recorded, in which the specimens under water were almost in- 
variably weaker. Table XIV., taken in connection with Mr. 
Rafter's tests, indicates, however, that mortars and concretes 
kept damp or under water are in general the stronger. The 
latter is the author's opinion. 

Wet or Dry Concretes — Table XV. shows results obtained 
from experiments made as thesis work by J. W. Sussex, published 



Art. 22.] 



ULTIMATE COMPRESSIVE RESISTANCE, 



131 



in the "Technograph" of the University of lUinois for 1903. The 
experiments were made to determine the relative strength of wet 
and dry concretes. The tests were made on forty-five six-inch 
cubes mixed with three different percentages of water and broken 
at the ages of seven days, one month and three months. The 
concrete was composed of one volume of Portland cement, three 

TABLE XV. 



Age 



Crushing Strength in Lbs. per Sq. In. 



Dry 



Lightly 
Tamped 



Heavily 
Tamped 



Medium 



Lightly 
Tamped 



Heavily 
Tamped 



Wet 



7 Days . . 
I Month . 
3 Months 



1200 
1750 
2300 



1340 
I960 
2600 



2280 
2290 
2130 



1330 
2360 
2390 



1040 
2230 
3040 



volumes of sand containing a small percentage of fine gravel and 
six volumes of crushed limestone. Tests were made with the 
three degrees of plasticity noted, and also with two degrees of 
tamping — light and hard. Each result shown is an average of 
three tests. At the end of three months it will be seen that the 
wet concretes furnished the greatest ultimate resistance, although 

TABLE XVL 



Kind of Cement and Sand 


Age in 
Days 


Ultimate Compressive Resistance in Lbs. 
per Sq. In. When Mixed 




Dry 


Medium 


Wet 


Portland; Bar Sand 

White " 

Natural ; Bar " 

White " 

Portland ; Bar " 

White " 

Natural ; Bar " 

White " 


7 
7 
7 
7 

28 
28 
28 
28 


1330 

1630 

238 

427 

2360 

2360 

481 

708 


1230 

1300 

292 

233 

1890 

2470 

307 

470 


1243 

1430 

328 

138 

1320 

1340 

334 

282 



at the end of seven days and one month the medium specimens 
furnished the highest ultimate resistance, whether tamped lightly 
or hard. 

T. L. Doyle and E. R. Justice record in "Engineering News" 
for July 30, 1903, the ultimate compressive resistances of six-inch 
cubes made with both Alpha Portland and Hoffman natural ce- 



132 



COMPRESSIVE PROPERTIES, 



[Ch. VI. 



ments and mixed to three different consistencies. Two kinds of 
sand, white sand and bar sand, were used, and the stone was one- 
inch trap rock. The ages of the specimens were seven and 
twenty-eight days. Table XVI. shows the results obtained, each 
figure being an average of five tests. It will be seen that in all 
cases the dry specimens furnished higher ultimate resistances 
than either of the other two kinds. The age of the specimens is 
not sufificient to show whether the wet mixtures would not ulti- 
mately be stronger than the dry. 

High Temperatures — The effect of high temperatures on ce- 
ment mixtures has not been studied to any extent as yet, but 
Table XVII., which is taken from the Watertown Arsenal Re- 
port for 1902, shows the variation in the ultimate crushing 
strength of four-inch cubes after they had been heated to differ- 
ent temperatures. The age of the cubes was, in most cases, 

TABLE XVII. 

Composition 



Cement 



Alpha* 

Alphat 

Dyckerhoff*. 

Mankato* ... 

t ... 





Ultimate Crushing Strength 


in Lbs. per Sq. In. 




After Heating to 


Sand 


Not 


200° 


300° 


400° 


500° 


600° 


700° 


800° 


Heated 


F. 


F. 


F. 


F. 


F. 


F. 


F. 


— 


9167 


8830 


7920 


9190 


9400 


9333 


8217 


8060 


— 


12480 


14447 


13853 


13767 


13910 


12787 


12130 


9985 


— 


5017 










4313 


3483 


4280 


— 


1867 


1657 


1876 


1966 


1603 


1453 


1496 


1400 


— 


3873 


4043 


3523 


3810 


4133 


4013 


3957 


3900 


1 


538 


491 


432 




471 




381 




1 


2170 


2067 


1953 




2063 




2240 





900° 
F. 

6060 



1185 

2990 

317 

1767 



*Cubes set in air before heating. tCubes set in water before heating. 

slightly over one year, and they were tested, usually, about thirty 
days after having been heated. Each result is an average of 
three tests. It w^ill be seen that there is practically no decrease 
in strength, even up to a temperature of 600 degrees Fahr., but 
a decrease is shown for higher temperatures. 



Art. 23. — Compressive Properties. 

Conduswns. 

It has seemed to the author that the graphical method used in 
determining the straight-line formula for long columns was the 
most rational way to combine the experiments which have been 
recorded in the preceding pages. Two sets of straight-line dia- 



Art. 230 



ULTIMATE COMPRESSIVE RESISTANCE. 



133 



grams have, therefore, been prepared, one showing the relation 
between ultimate compressive stress and the compressive coeffi- 
cient of elasticity, and the other showing the relation between 
ultimate compressive resistance and the parts of cement to aggre- 
gate in the mixture. The question of age has been entirely ex- 
cluded, since very little material under three months of age was 
used, and it has previously been shown that mixtures do not gain 
appreciably in strength after that period. The figures otherwise 

6,000,000 



I 

£ 5,000,000 



C 4.000,000 



n 

^ 3,000,000 



2,000,000 



















































/ 






























/ 




























/ 


f 
























X 




' 




























7 


























^ 


/- 


: 
























<9 


/- 
























.^' 


/" 


























■■■<y 


7 


X 






















^ 


f" 


/ 


























J 


'/ 


























i 


/ 


X 


























/ 






























/ 













































































































































































FIG. 1. 



1000 2000 3000 

Ultimate Crushing Resistance Lbs. per Sq. In. 

FROM BACH'S TESTS.— TABLE I., ART. 21. 



need but little explanation; each represents graphically one of the 
tables which have been recorded in the previous pages. Tables 
III., IV., V. and VI. of Art. 21 have not been included, since the 
values there shown are not the true or elastic coefficients; Table 
VII. has not been included on account of the limited number of 
tests. 

There has also been included in Figure 8 a summary of the 
tests made at the Watertown Arsenal in 1899 on twelve-inch con- 
crete cubes varying in age from one to six months. The tests 



134 



COMPRESSIVE PROPERTIES. 



[Ch. VI. 



were made with five well known brands of Portland cement, with 
various mixtures of sand and stone. 

The tests made by Messrs. Derleth and Hawkesworth were not 
sufficient in number to enable their results to be included in a 
figure. 



p. 

oS 1,000,000 

S 
1 



; 8,000,000 























































































( 




























/ 






























/ 


























X 


/ 




























> 


/ 




























/ 




























"/ 


l/ 


























t 


/ 




























-f 


f^ 


























c 


V 
&/ 




























i 


X 


























X 


/ 


X 




























r 



















1000 2000 

Ultimate Crushing Resistance Lbs. per sq. in. 

FIG. 2.— FROM BACH'S TESTS.-TABLE II., ART. 21. 



Figures i to 9 represent the variation of the coefficient of elas- 
ticity with the variation of the ultimate compressive resistance. 
The equations of the lines there shown are as follows, / represent- 
ing the ultimate compressive resistance : 

^==1,520,000+1900/ ' (Bach) Fig. I. 

E=i o +1820/ (Bach) Fig. 2. 

Ez= o +1000/ Fig. 3. 

^= o +1090/ Fig. 4. 

Ez=z o -f-1600/ (Hatt) Fig. 5. 

E=. o +1570/ (Austrian) Fig. 6. 

E=. 62,000+ 794/ (Rafter) Fig. 7. 

Ez=i o +1150/ Fig. 8. 

Ez=z o +1000/ (McCaustland) Fig. 9. 



Art. 23.] 



ULTIMATE COMPRESSIVE RESISTANCE, 



135 



Averaging- the nine different numerical expressions which 
these figures furnish, it will be found that an average value of 
the compressive coefficient of elasticity may be expressed by the 
equation 

^=175,000+1325^ 

in which p represents the ultimate compressive resistance. The 
constant quantity, 175,000, is negligible in relation to the other 
and may be neglected with very 53,000,000 " 

little error, so that a simpler f 
form of expression is the fol- J 
lowing: 

^=1325/- 

The constant 175,000 may be 
neglected with all the more 
safety since it depends mainly 
on one series of experiments, 
Professor Bach's, and in 



«3 2,000,000 



a> 
01,000,000 









/. 








t 




/ 






/ 


r 

X 







VYL 



1000 2000 3000 

Ult. Comp. Strength in Lbs. per sq. in. 

these experiments the coeffi- fig. 3.-eastern expanded metal- 

^ , , ,11.1 CO.'S TESTS.— FROM TABLE 

cients are undoubtedly higher vn., art. 21. 

than in other cases, on account of the repeated application of 

every load. 

In a similar way, Figures 10 to 15 represent the variation of 
the ultimate crushing resistance with the variation in the ratio of 
the cement to aggregate; the following equations are then ob- 
tained: 

/=475o — 250 w (Bach) Fig. 10. 

/— 5140 — 238^ (Rafter) Fig. 11. 

^=4578 — 289^^ (Rafter) Fig. 12. 

^=3835 — 2oym. .(Watertown, Table V.) Fig. 13. 

/i=3440 — 280 w (McCaustland) Fig. 14. 

^=5035 — 2i^m (Watertown, 1899) Fig. 15. 

Henby's tests (page 112) in addition furnish an equation of 

/=435o— 258^2. 
The average of all these equations furnishes 

/=4449— 247W, 
in which / equals the ultimate crushing resistance and m the 



136 



COMPRESSIVE PROPERTIES. 



[Ch. VI. 



9,000,000 



8,000,000 



C 7,000,000 



a 6,000,000 
•J 

c 

^ 5,000,000 



° 4,000,000 

I 
« 

I 

§ 3,000,000 

2,000,000 

1,000,000 

1000 2000 -MOO 4000 5000 6000 

int. Comp. Strength In Lbs. per sq. In. 
FIG. 4.— WATERTOWN, 1898» TESTS.— TABLE VIII., ART. 21. 









X X 


X ^ 





















X 


/ 


/ 








4 


V 


Jl 










v/^ 












- 


/ 










X 


/ 


f 








/ 


/ 




c 






/ 













5,000,000 r 



^' 5,000,000 



^4,000,000 

■ e 
iS 3,000,000 



o 2,000,000 



; 1,000,000 



1000 2000 3000 4000 "o iqOO 2000 3000 4000 

Ult. Comp. Strength in Lbs. per sq. in. xnt. Comp. Strength Lbs. per sq. in. 

FIG. 5. FIG. 6. 

HATT'S TESTS.— TABLES VI. AND AUSTRIAN SOCIETY'S TESTS.— TABLE IX., 
VII., PAGES 83 AND 84. PAGE 96. 









/ 






x/ 

> / 


' 




-^ 


/ ^ 

/ ^ 






X / 






/ 








/ 










Art. 23.] 



ULTIMATE COMPRESSIVE RESISTANCE, 



137 









































i 






















































































t 




























X 














a 


3,0( 


>0.00 

























V 


/" 


X 










M 

^ 


























^/^' 


/ 














C >- 
















X 




** 




y 


/ 














. jo 






















^ 










^ 










1' 
















.. 


/i^' 


! 


X 


X 
















2,0( 


)0,00 







'. 




X 


^-^ 


X 






















a 












^-" 
















X 




















^ 


y 




X 








X 
















a 






X 


■/ 


/ 




^ 






X 




























/ 


X 


* 











































































1000 



2000 3000 1000 

Ult. Crush Load in lbs, per sq. in. 



-5000 















FIG. 


7.- 


-RAFTER'S TESTS 


—TABLE 


IX. 


, ART. 


21 


• 














5,0< 


0,00 


() 
















































































































































/ 






















































/ 


/ 


















4,0( 


0,00 

























X 


X X 


X 




/ 


/^ 




















































/ 


/ 




















J3 
fi 
































/ 


/ 






















(-1 
























X 




X 




/ 


X 


















X 


X 


5S 






























/ 


























;4 


3,0< 


0,00 


() 














X 






X 


/ 


XX 
















X 






X 




EC 

s 

1 

a 


























/ 




















































7 


/xxx 


X 












X 


































,c 


;^/ 


^ 












X 




















S 












X 










K. 












X 




X 




















8,0( 


0,00 


) 




) 






X 


t-l 


[/ 






X 


























X 




w 

4-1 
















X 


/ 






































^ 










X 




X X 
V 


/I 








































1 










XX 




/ 










































a 












/ 














































IjOi 


0,00 


) 




/ 


'x 


X 














































/ 


/ X 






















































/ 

























































































































































































































1,000 2,000 3,000 4,000 5,000 

Ultimate Crushing Resistance in Pounds per Square Inch 
FIG. 8.— WATERTOWN, 1899, TESTS OF FIVE WELL-KNOWN BRANDS 
OF PORTLAND CEMENT. 



138 



COMPRESSIVE PROPERTIES. 



[Ch. VI. 



ratio of aggregate to cement. This equation may be used with 
safety to determine the strength of any mixture, with m between 
the limits of 4 and 16. 

The question of the uhimate strength of cement mixtures has 

5,ooo,ooo| \ \ 1 1 been considered by the author 

from one point of view only, viz., 
<» 4,000,000 



a 3,000,000 



A 2,000,000 



1^ 



c 
|l,000,000 

o 

o 









X 




> 


X 


/ 




^5 






■* 








/ 









§15 



10 



1000 2000 3000 41)00 

Ult. Conip. Strength in Lbs. pei- sq. in. 



\ 














X 








X 

> 


X >^< 






K 


X 


'X 


\ 



FIG. 9. 

McCAUSTLAND'S TESTS. 

FROM TABLE X., ART. 21. 



low 2000 3000 4000 

Ult. Crush. Resist, in Lbs. per sq. in. 

FIG. 10.— BACH'S 1896 TESTS, ON 10-IN. 

CYLINDERS, 10 INS. HIGH. 

TABLE II., ART. 21. 



the relation between the cement to the aggregate. Another 
method of dealing with this question has, however, been studied 
by R. Feret in Europe, and is being studied by William B. Fuller 
20 1 — \ — \ — I w I — I — ] — \ — \ — \ — r in America; the latter's results 

are not yet published. This 



cl8 

I 16 



12 



TslO 

be 

< 6 









y> 


y — 




















X) 


X 




















V 


\( 


A 




















X 


\\] 


'% 




















XXx 


^ 


> 




















' 


o\ 


^'^. 






















\ 


St 




















X 


s 


^. 






















S 

























CO <ul2 



fioio 

:• o 

.*S4J 



00 



as 

as 



1000 2000 3000 4000 5000 
Ult. Crush. Resist, in Lbs. per Sq.In. 

FIG. 11. 

RAFTER'S TESTS. 

FROM TABLE I., ART. 22. 















^Slpx 










>J 




X 
< 








A 




X 

1 



IOIjO 20uO 3U0« 4Uoo 

Ult. Crush. Resist, in Lbs. per sq. in. 

FIG. 12. 
RAFTER'S TESTS. 
FROM TABLE IV., ART. 22. 



method considers not merely the relation between the cement 
and the aggregate, but also the balancing of the entire mixture. 



Art. 23.] 



ULTIMATE COMPRESSIVE RESISTANCE. 



139 



R. Feret, for instance, has shown that the ultimate resistance 
to compression of 1 13 mortar blocks, in which the sand was com- 
posed of varying proportions of the three graded sizes of sand 
which have been previously noted in some of his tests, varies 
from some miinimum value to a value perhaps three times as 
large, depending merely on the proportions of the various sizes 



12 

-g 10 

ho 
™c 

00*^4 
,? 2 



1000 2vW0 3000 

Ult. Crush. Resist, in Lbs. 
per sq. in. 

FiG. 13. 

WATERTOWN TESTS. 

FROM TABLE V., ART. 22. 





•V t 


'"-^ 




"-^ 






'^ 















c 15 



10 















AN 










^■"i 




. ' 





1000 2000 3000 ±000 

Ult. Crush. Strength in Lbs. per sq. in. 
FIG 14.— McCAUSTLAND'S TESTS. 
FROM TABLE X., ART. 21. 



of sand. This variation in strength is in proportion to the varia- 
tion of the solid material in the mass, the maximum value being 
obtained when the medium sized grains are eliminated. This 
was found to hold true no matter under what conditions the mor- 



20 

g 
« 15 



10 



"^ 


Alsen 












— 


















"^^ 


^<^.> .^^, 


Say 


or's 


























Gei 


•man 


ia^- 


^-^ 


S; 


■O" 


•-. 


p=5 


035- 


214 n 


.. 


























s';^ 


^ 


■^^ 


^Atlas 






























"'j 






IS 




All 


ha 




























'^ <> 


[i^^ 

ie^ 


^ 


!___ 


~-x 


































^^f^ 


-^^ 


. 


































^ 




~-^ ~ 


-X 




1000 



5000 



2000 3000 4000 

Crushing Resistance in Lbs. per sq. in. 

FIG. 15.— WATERTOWN, 1899, TESTS ON FIVE WELL-KNOWN BRANDS 
OF PORTLAND CEMENTS. 

tars were allowed to set and harden. Feret cites numerous ex- 
amples, but Figures i6 and 17 are characteristic of all his experi- 
ments. In this case the percentages of the various sizes of sand 
grains are represented on the perpendiculars erected on the sides 



140 



COMPRESSIVE PROPERTIES. 



[Ch. VI. 



of an equilateral triangle, a system of co-ordination which is 
familiar. The ultimate crushing resistance of the various mor- 
tars is marked at the proper points within the triangle ; with these 
points as guides, contour lines, representing mixtures having an 
equal ultimate resistance, are then drawn. 

Figure i6 shows very clearly how the strength of the mixture 
increases as the medium sized grains are eliminated. 

Figure 17 was drawn in a similar manner, but represents the 
relation of solid matter to the total cubic contents in a freshly 
mixed mortar. The close similarity between these two figures 



1 :3 Mortar, 9 
months in air, 
3 months in sea 
water. 




1:3 Mortar 
(freshly mixed) 




G 4400 F 

Note: The letters G, M, F, indicate large, 
medium and fine grains of sand. 

FIG. 16. 



FIG. 17, 



Showing Proportion of Solid Matter to Total Cubic 
Contents of Mortars Mixed with Differing Per- 
centages of Various Sized Sand. 



Showing the Ultimate Compressive Resistances, 
in Lbs. per Sq. In., of Mortars, Mixed with 
Differing Percentages of Various Sized Sand. 

is noticeable and checks Feret's conclusion that the ultimate 
compressive resistance varies in proportion to the solid matter 
in a specimen. It will require much work of this character in 
order that some definite conclusions may be obtained. 

Considering in general all the tests which have been tabulated, 
it may be concluded: 

First — That concretes in compression have a point that may 
be termed the elastic limit, and its value is between one-half and 
two-thirds of the ultimate resistance. 

Second — That up to this elastic limit the compressive coeffi- 
cient of elasticity may have in general a value of 1325 times the 
ultimate crushing resistance. 



Art. 23.] ULTIMATE COMPRESSIVE RESISTANCE, 14 1 

Third — That, within certain Hmits, the ultimate crushing re- 
sistance for cement mixtures over three months old may be ex- 
pressed by the equation 

/^4449— 247»?, 

in which p represents the ultimate crushing intensity and m the 
number of parts of aggregate to one part of cement. 

Fourth — That concretes mixed dry and thoroughly tamped are 
slightly stronger than those mixed wet; but in actual construc- 
tion work other considerations besides the slight increase in 
strength may offset this advantage which appears in favor of the 
dry concretes. 

Fifth — That concretes hardening under water attain slightly 
greater ultimate resistance than the same mixtures hardening in 
air. 

Sixth — That temperatures below 6oo degrees Fahr. do not af- 
fect adversely the strength of concretes. . 

It has been shown that there is no appreciable increase in 
strength after the material is three months old. Therefore, if it 
is desired that a concrete should possess ultimately a high value 
of the coefficient of elasticity, it is possible to obtain it only by 
using richer mixtures. 

And, finally, it appears that the values of the coefficients of 
elasticity for tension and compression are practically equal. 



CHAPTER VII. 



FLEXURAL PROPERTIES. 



Art. 24.— The Theory of Flexure as Applied to Concrete. 

Careful consideration must be given to the theory of flexure in 
connection with concrete beams in flexure. In determining the 
coefficient of elasticity for flexure two conditions in the theory of 
flexure are usually assumed, viz., that the coefficients of elasticity 
for direct tension and direct compression are equal, and that they 
are constant. This is rarely, if ever, the case ; but in order to de- 
termine the deflections of beams it is necessary to make these as- 
sumptions in order to determine the empirical value for the flex- 
ural coefficient of elasticity. It has been shown that neither of 
these assumptions holds precisely for concrete, and that, therefore, 




T""T 



I 

c2, 



-N- 



.i._ 



FIG. 1. 

the value of the coefficient of elasticity which may be deduced for 
bending has no reasonable basis; but it seems to be perfectly 
proper to determine it as an empirical quantity, since it is a pos- 
sible way in which to determine in advance the deflection of these 
concrete beams. 

The quantity, which is usually called the modulus of rupture, 
or the extreme fibre stress at rupture, is probably as correct a 
quantity for concrete as in the case of any other material, even 
such as steel or wrought iron. This modulus of rupture is de- 



Art. 24.] THE THEORY OF FLEXURE. 143 

termined from the theory of flexure, on the assumption that the 
stress in any fibre at a section of the beam varies directly as the 
distance from the neutral axis of the beam. At the time of rup- 
ture this does not hold true for steel, for wood, for concrete or 
for any substance whatsoever. This value, therefore, is not cor- 
rect for any material, but it is of the greatest value in the design 
of beams. 

The writer has discussed the analytic treatment of concrete 
beams fully in another place,* and it is therefore unnecessary to 
repeat that treatment here; but the following analysis for finding 
the deflection of a beam composed of a material having unequal 
coefficients of elasticity for tension and compression is of con- 
siderable interest on account of the simplicity of the final equa- 
tions. Let Figure i represent the cross section of a beam of 
such a material, NN representing the neutral axis as determined 
in some possible way. 

The following notation will be used: 

/=iintensity of stress at units distance from NN; 

^=the distance of any elementary area dA, from NN; 

z/=the unit strain corresponding to /; 

Et and ^c=the coefficients of elasticity of the materials for ten- 
sion and compression respectively; 

At and ^c=the areas at any section which carry tension and 
compression respectively; 

It and /c=:the moments of inertia of At and Ac respectively about 
NN as an axis. 
From the general theory of flexure, the moment of the stress 

acting on the differential area dA, distant z from NN, about that 

axis is: 

z .p .dA . zr=Eik . zK dA. 

The differential internal moment, integrated over the entire 
section, becomes equal to M, the external moment: 



M-. 



^^ z\ dAc+Et . /.J ^ z\ dAt . . . (l) 
^=Ec . Ic . /A+^? ' It - l^ (2) 



Trans. Am. Soc. C. E., Dec, igoj. 



1 4 4 FLEXURAL PROPERTIES, [Ch. V 1 1 . 

//'^ 
But /*= — = — -, if p represents the radius of curvature of the 

neutral axis; therefore 

d'^i^ ^ ^ d^'io 

M^Ec.Ic- ~—-\-Et.It.^~- 

dor dx' 

d'^in M , . 

or, = (3) 

dx^ EcIc-\-EtIt 

If ^c=-5'^, then = — where / represents the moment of 

dx" EI 

inertia of the entire section about NN. 

By the aid of Eq. 3, it would be possible to determine both Et 
and Eq, by means of the deflections found under two different 
loads, provided the position of the neutral axis could be deter- 
mined. To determine the neutral axis it becomes necessary to 
know in advance, or to assume, both Et and Ec If assumed, 
the correctness of these values must then afterward be checked 
by means of the deflections. 

To pass through such a procedure becomes a tedious task, 
more especially, as has been shown, that Et and Ec for concrete 
do not differ greatly, if at all. In all his work the author there- 
fore has calculated the apparent flexural coefficient of elasticity, 
assuming Et equal to Ec. 

Since concrete beams show permanent deflections under com- 
paratively light loads, it also becomes necessary, as in the case of 
pure compression, to distinguish between the elastic coefficient 
and one calculated from the total strains only. 

Art. 25. — Flexural CoeflBlcient of Elasticity. 

Table I. and Figure i are taken from a paper by the author and 
recorded in the Transactions of the American Society of Civil En- 
gineers, 1903. The table shows the values of the flexural coeffi- 
cient of elasticity and of the extreme fibre stress for concrete 
beams 4x4 inches X36 inches span, tested to destruction by a 
centre load. The table is of interest on account of the age of the 
specimens tested, which was seven and one-third years. The 
mixtures used are given in the table; the sand was Cow Bay, L. I., 



Art. 25.] FLEXURAL COEFFICIENT OF ELASTICITY, 



145 



and the gravel was rounded, varying in diameter from J to 2-J 
inches ; it was well washed before being used. 

Figure i shows the deflections at the centres of the different 
specimens. The deflections of each bar are represented by two 




0.002 



0.006 0.010 O.Oli 0.018 
Deflection at Center, in Inches 



0.022 



0.002 o.ooe 0.010 0.011 0.018 

Deflection at Center, in Inches 



FIG. 1. 



curves lettered with the same subscript. The curve to the left 
shows the set when the load at that given point was entirely re- 
moved. It was found that the true or elastic coefficients of elas- 



146 



FLEXURAL PROPERTIES. 



[Ch.VII. 



ticity, calculated in the way which has already been explained, 
gave constant values for the coefficient for any one specimen al- 
most up to the breaking load. The table shows that neither the 
coefficient nor the ultimate strength shows any remarkable in- 



TABLE I. 



Bar 


Age 

in 

Years 


Span 

in 
Inches 


Section of Bar 
in Inches 


Coefficient of 

Elasticity in 

Lbs. per Sq. In. 


Extreme Fibre 
Stress in 




Depth 


Width 


Lbs. per Sq. In. 


A 

A,.... 
A,.... 

B 

B,.... 
B,.... 

c... 

D.... 


7.4 

7.4 

7.4 

7 

7 

7 

7 

7 

7 

7.3 

7.3 

7.3 


36 
16 
16 
36 
16 
16 
36 
16 
16 
36 
16 
16 


4.12 
4.12 
4.12 
4.12 
4.12 
4.12 
4.12 
4.12 
4.12 
4.10 
4.10 
4.10 


4.06 
4.06 
4.06 
4.00 
4.00 
4.00 
4.05 
4.05 
4.05 
4.15 
4.15 
4.15 






1,591,000 

1,102,000 

2,122,000 

2,440,000 

1,220,000 

1,315,000 

387,000 

1,023,000 

1,165,000 

597,000 

597,000 


278 
315 
606 
636 
530 
247 
229 
208 
294 
415 
346 



Bars A=l Aalborg cement, 2 sand and 4 gravel. 
" B— 1 Atlas cement and 3 sand. 
*' C=l Alsen cement, 3 sand and 5 gravel. 
" D=l Alsen cement and 2 sand. 

crease for very old specimens. They may increase for beams 
less than one year old, but for bars of the age shown in the table 
neither of the constants shows any material increase. 

In discussing these experiments Professor E. J. McCaustland 

TABLE 11. 



Specimen No. 


Brand 


Coefficient of Elasticity 
in Lbs. per Sq. In. 


Extreme Fibre Stress 
in Lbs. per Sq. In. 


T ... 


Cayuga Lake. 

// It 
Empire Portland. . • 

ti t4 




571 

357 
238 
190 


2 


1,384,000 

600,000 

460,000 

1,219,000 

1,582,000 

920,000 


3 

4 


5 


623 


6 


618 


7 


452 





records in the same Transactions some experiments made by him 
on neat cement beams 2x2f inches deep X24 inches span, one 
year old, tested by centre loads. 
Table IL shows results of the constants determined in the same 



Art. 25.] FLEXURAL COEFFICIENT OF ELASTICITY, 147 

manner as in the preceding table. It is to be noted that the co- 
efficient of elasticity increases with the increase of the extreme 
fibre stress. The stress-strain curves shown by Professor Mc- 
Caustland are exactly similar to those of Figure i and need not 
be reproduced. 

In the same discussion Professor G. Lanza records results of 
experiments on one plain and twenty-six reinforced concrete 
beams 8x12 inches xii foot span. 

At this point it is only necessary to introduce the results of the 
neat specimen, since the others must be analyzed by a theory of 
flexure, which is not a part of the present discussion. 

For the plain concrete beam, whose age was forty days, the 
value of the extreme fibre stress was found to be 170 pounds per 
square inch, the composition of the concrete being one part Port- 
land cement, three parts sand, four parts of trap rock passing a 
one-inch ring sieve, and two parts ot the same rock passing a J- 
inch ring sieve, all proportions being measured by volume. 

Jules A. Coelos and R. A. W. Carleton, graduating students of 
the Civil Engineering course at Columbia University, 1904, per- 
formed during the winter of 1903-04 an extended series of tests 
on plain and reinforced concrete beams 6x6 inches in cross sec- 
tion, tested on a span of 36 inches. The materials which were 
used were exactly the same as those used in the direct tension 
and compression tests recorded previously on page 84 in the ex- 
periments of Messrs. Derleth and Hawkesworth, and need no 
further explanation. 

The loading was either a single centre loading or was placed 
at two points symmetrically distant from the centre of the span. 
The deflections were read in the centre of the beam in the same 
manner as the tests which were recorded in Table I., and the co- 
efficient of elasticity was calculated as the true coefficient. 

Only the plain concrete beams are given in Table III. Tests 
of the ultimate shearing resistance of the bars were made after 
they had been broken, and these values are also given in the 
table. 

W. L. Brown has recorded in the Proceedings of the Institu- 
tion of Civil Engineers, 1898- 1899, a series of tests on cross 



148 



FLEXURAL PROPERTIES, 



[Ch. VII. 



bending of neat cement and mortar mixtures. The size of the 
specimens was always 2 inches deep by i inch wide by 30 inches 
span. Three kinds of sand were used — a good ordinary coarse 
red sand, well washed; a poor argillaceous fine sand, unwashed, 
and a fine Laxey gravel, which was really a very coarse sand. 

Two sets of experiments were made, using two brands of ce- 
ment. The deflections were measured at the centre of the beams, 
the loads being placed at the same points. The coefficients of 
elasticity were determined from the formula of the common the- 
ory of flexure and calculated between the extreme limits of stress 
obtained. The breaking load varied from a centre load of 5 to 35 

TABLE III.— FLEXURAL TESTS ON 1:3:5 PORTLAND CEMENT 
CONCRETE BEAMS, 6x6x36 INCH SPAN. 



No. 


Age in 
Days 


Loading 


Coefficient of 

Elasticity in 

Lbs. per 

Sq. In. 


Net Fibre 

Stress 

Lbs. per Sq. In. 


Shearing Tests 

Shearing Intensity in Lbs. 

per Sq. In. 




At First Crack 


At Failure 


I 

2 

5 

7 

8 

21 


127 

128 

128 
125 
141 

121 


At 2 Points 
At Centre 


1,118,900 

1,002,300 

1,440,900 
2,161,500 
1,012,500 

1,205,500 


170 

218 

189 
225 
148 

223 


180 

r 118 
1153 

lOI 

167 
r 97 
I 86 


1256 
1 196 
1 178 
1 180 
f 168 
1255 
214 


r330 
1226 



pounds. On account of the small sizes of the specimens and on 
account of some ambiguity in the methods of calculation, it has 
been thought better not to give here in detail the experiments 
themselves, but merely Mr. Brown's general conclusions: 

That E is greater for neat cements than for mortars; that E 
varies inversely with the amotmt of sand in a specimen; that the 
quality of sand affects E, but not considerably, but that age does 
increase ^ to a measurable extent. 

Some experiments on the coefficient of elasticity of concrete 
beams have been recorded by Durand-Claye in "Annales des 
Fonts et Chaussees," 1888, and are here shown in Table IV. 
Tests were made on seven bars; six were neat Portland cement 



■ V « -^r ••■ ■ - 
ft*- « ^ ^■ 

■ #■. aig^.#» . #► /«■ ^ 4^ «> -v -. 



D 


On 








3 


cs 


D. 


3 




o 




7) 


CA) 








o 


1 
o 


3 


3- 


n 

o 


m 


3 




o 


n 


-5 
(Tl 






3 


f5 






-s 




f» 


"* 


O 


H 




M 


C/3 


cr 


T3 


n 







Art. 26.] 



MODULUS OF RUPTURE IN BENDING, 



149 



and one was 1:2 mortar. The prisms were approximately 1.2 
inches square, tested on a span of 39.4 inches ; it does not appear 
that the sets remaining after the loads were removed were meas- 
ured, so that the values given in the table are not the elastic 
coefficients. 

It is seen, therefore, that the coefficient increases with the 
value of the extreme fibre stress, and acts, therefore, similarly to 

TABLE III. 



Composition in 
Parts by Weight 


Age When 
Tested 


How Kept 


Coefficient of 

Elasticity in 

Lbs. per Sq. In. 


Extreme 

Fibre 

Stress in 

Lbs. per 

Sq. In. 


Net Tensile 
Resistance 
of Similar 
Specimens 

in Lbs. 
per Sq. In. 


Cement 


Sand 


Neat 




5 to 6 Weeks 

6 Months 
2 


Under Water 
In Air 


3,380,000 
3,370,000 
2,810,000 
3,410,000 
3,340,000 
3,860,000 
3,410,000 


1000 
950 
781 

1020 
923 

1090 
370 


880 
823 
667 
824 
780 
950 
270 


" 




,, 




tt 




I 


2 



pure tension or compression; its value does not appear to differ 
greatly from that found in those cases. 

Art. 26. — Modulus of Rupture in Bending. 

Table I. gives the results of flexural tests on iii concrete 
beams, as reported by E. S. Wheeler in the Report of the Chief 
of Engineers, U. S. Army, for 1895, P- 2922. The specimens 
were all 10 inches square and 4J feet long, broken on a 4-foot 
span, with a centre load. In general the bars were kept covered 
with moist earth, awaiting the time of breaking. The age of the 
beams was between six months and two years. It will be seen 
that there is considerable difference in the strength of those 
beams when the stone used was sandstone or limestone. In 
almost every case the limestone furnished higher values of the 
modulus of rupture. The tests included beams mixed with both 
Portland and natural cements. Figs, i and 2 are plotted from the 
table, the ordinates being the extreme fibre stresses of the beams 
and the abscissae being the ratios by volume of the aggregate 
(the sand and stone) to the cement. No attention was paid in 



150 



FLEXURAL PROPERTIES, 



[Ch. VII. 



the figures to the difference in age of the various specimens, but 
tests No'S. 98 to III were not plotted. A straight Hne was drawn 






2 2 



20 

19 

18 

17 

16 

15 

14 

13 

12 

11 

10 

9 

8 

7 

C 

5 


















































1 


1 1 






~ 




~ 






































































































^ 




X 




X 










































































K 


N 
















































































r\ 






'5 






'= 




































































^ 








X 


• 


































































X 




> 


N 


X 


''I 






































































X 


X 


S 


^ 


t<%-. 




















































1 




X 












/ 






















































































<^ 


6> 






















































XX 


> 


> 




1 
















^ 


\ 






X 
































































> 










"v 


^ 
















































































^ 


\ 










































































X 






\ 


V 


X 














































































\, 


































































X 








* 
































j_ 








1 










































X 












X 


1 
3 

2 


1 


- 














' 1 
























































































































- 


— 


" 


lJ 


— 


— 


- 






































- 






















(\. 




L 






L_.. 






1 













































100 



coo 



700 750 



200 300 400 500 

Extreme Fiber Stress in lbs. per sq. in. 
FIG. 1.— TESTS ON PORTLAND CEMENT BEAMS BY E. S.WHEELER. 

to average as nearly as possible the results as plotted; the equa- 
tion of the lines for Portland cement mixtures was found to be : 

^=840 — 37.67 
and for natural cements 

^=1526 — 42.67. 

Using these lines as a basis, it will be seen that the greatest pos- 
sible modulus of rupture which can be obtained is for the neat 



fee 

to 

< i 

o ^ 

*- C 
a o 



CIS 



S^ 5 

1^4- 
oS£. 3 

•= 1 



























' 
























































■ 




































































— 




-"^ 


\ 










































■■«. 


^, 


) 








X 










































^. 




















































" 


^ 


.^ 




















































'"'" 


^j 


^S 


^ff 














































•* 




\ 


'^i 


V. 


















































s?> 


\^ 




X 
















































•n 


.^ 




















































X 










X 



























































































































































13 100 200 300 400 500 

^ Extreme Fiber Stress ta lbs. per sq. in. 

FIG. 2.— TESTS ON NATURAL CEMENT BEAMS BY E. S. WHEELER. 



cement, and is respectively 840 and 526 lbs. per square inch for 
the Portland and natural. These values decrease steadily as the 



Aft. 26.] 



MODULUS 0^ RVPfURE IN BENDim. 



iSl 



TABLE l. 





Proportionate Parts 






)er Cu. 
I Con- 
When 
en 


u e 




by Volume 






Age 


<o\z " 








Kind of Stone 


When 


Ec««5 cT 




Cement 


Sand 


Gravel 




Broken 


Wt. r 

Ft. ol 
Crete 
Brok 


Extr( 
Fibre 
in Lb 
per S 


%z 


1 Portland 


1.24 


3.0 


Limestone 


2 Years 


153 


597 


23 


" 


1.67 


4.0 


" 


" 


155 


551 


24. ••■ 


<( 


1.67 


4.0 


It 


6 Months. 


155 


465 


25 


1 Natural 


1.78 


4.18 


Sandstone 


1 Year 


136 


124 


26 


" 


1.78 


4.18 


Limestone 




148 


150 


87 


<( 


1.78 


4.18 


11 




140 


242 


28 


( 


2.16 


4.18 


Sandstone 




140 


94 


29 •••. 


(( 


2.16 


4.18 


Limestone 




141 


96 


30 


(( 


2.16 


4.18 


II 




139 


204 


31 


I Portland 


3.14 


7.61 


Sandstone and Gravel 




144 


219 


32 


" 


3.14 


7.61 


Limestone and Gravel 




151 


239 


33 


(1 


3.14 


7.61 


Gravel 




150 


192 


34 


<i 


3.14 


7.61 


Limestone and Gravel 




143 


185 


35 


t( 


3.12 


9.52 


Gravel 




139 


139 


36 


<( 


3.12 


9.52 


Limestone 




141 


169 


37 


<( 


3i07 


9.52 


" 




144 


283 


38 


(1 


3.08 


7.61 


CI 




148 


422 


39 


" 


3.08 


6.34 


<l 




148 


374 


40 


<i 


3.07 


9.52 


U 




143 


285 


41 


" 


3.08 


7.61 


IC 




139 


279 


42 


<( 


3.18 


11.42 


<| 




145 


247 


43 


i( 


3.18 


6.34 


<c 




140 


319 


44 


It 


3.18 


11.42 


Limestone with Screenings 




141 


29S 


45 


1 Natural 


2i30 


8.23 


Gravel 




150 


120 


46 


" 


2.27 


6.86 


" 




151 


74 


47 


tt 


2.25 


10.17 


II 




146 


110 


48 


" 


2.27 


6.86 


Sandstone 




146 


123 


49 


<( 


2.25 


10.17 


" 




131 


74 


50 


i( 


1.87 


5.33 


" 




138 


181 


51 


u 


1.87 


5.33 


II 




139 


214 


52 


« 


1.87 


5.33 


11 




138 


175 


53 


1 Portland 


4.16 


13.9 


II 




133 


177 


54 


" 


4.16 


13.9 


11 




132 


213 


55 


it 


4.16 


13.9 


II 




132 


204 


56 


1 Natural 


1.50 


5.38 


II 




140 


194 


57 


" 


1.50 


5.38 


II 




136 


210 


58.. .. 


i< 


1.50 


5.38 


II 







— 


59 


I Portland 


5,2 


13.2 


II 




135 


193 


60 


(i 


5.2 


13.2 


II 




141 


221 


61 


» 


5.2 


13.2 


II 







— • 


62 


1 Natural 


1.12 


4.15 


II 




140 


275 


63 


" 


1.12 


4.15 


II 




137 


306 


64-. •• 


K 


1.12 


4.15 


II 




— 


— 


65 


1 Portland 


2il 


11.1 


it 




132 


255 


66 


tt 


2.1 


11.1 


ti 




134 


260 


67 


i( 


2.1 


11.1 


ii 




— 


— 


68 


It 


4.16 


12.4 


it 


20 Months 




357 


69 


*' 


4.16 


12.4 


1. 






288 


70 


*' 


3.12 


12.4 


ii 




— 


297 


71 


«( 


3.12 


12.4 


11 




— - 


351 


72 


(( 


2.08 


12.4 


II 




— 


326 


73 


ti 


2.08 


12.4 


II 




— - 


345 


74 


It 


1.04 


12.4 


II 


" 


— 


310 


75 .... 


II 


1.04 


12.4 


II 


II 


— - 


288 


76 


II 


0.00 


2.09 


II 


19 Months 


— 


582i 


77 


II 


0.00 


2.09 


II 


" 


— - 


603 


78 


11 


1.04 


3.76 


It 


" 


— 


652 


79 


" 


1.04 


3.76 


II 




— 


727 


80 


" 


2.08 


5.57 


" 


" 


— 


488 


81 


II 


2.08 


5.57 


II 


" 


— 


588 


82 ••.. 


II 


3.12 


7.71 ' 


II 


II 


— 


513 


83 


II 


3.12 


7.71 


II 


II 


— 


465 


84 


II 


4.16 


9.86 


II 


II 


— 


376 


85 




4.16 


9.86 


II 


II 


— 


382 



152 



FLEXURAL PROPERTIES, 



[Ch. VII. 









TABLE I. — Continued* 










Proportionate Parts 
by Volume 


Kind of Stone 


Age 
When 
Broken 


Wt. per Cu. 
Ft. of Con- 
crete When 
Broken 


me 

Stress 
s. 
q. In. 




Cement 


Sand 


Gravel 


Extre 
Fibre 
in Lb 
perS 


86 

87 

88 

89 

90 

91 

92 

93 

94 

95 

96 

97 

98*.... 
99*.... 

100 

101 

102t.... 
103t.... 
104$ ••.. 
105t ... 

106 

107 

108§ • • . 
109§ ... 

iioir.... 
iiiir.... 


1 Portland 

« 
<t 

1 Natural 

u 
u 
<( 
<i 

(t 

1 Portland 

C( 

<t 
(( 
t( 
(t 
(i 
(I 
« 
l( 
i( 
<t 
u 


5.20 
5.20 
6.24 
6.24 
0.75 
0.75 
1.50 
1.50 
2.25 
2.25 
3.00 
3.00 
2.08 
2.08 
2.08 
2.08 
2.08 
2,08 
2.08 
2.08 
2.08 
2.08 
2.08 
2.08 
2.08 
2.08 


11.93 
11.93 
13.80 
13.80 
3.05 
3.05 
4.06 
4.06 
5.90 
5.90 
7.40 
7.40 
5.64 
5.64 
5.64 
5.64 
5.64 
5.64 
5.64 
5.64 
5.64 
5.64 
5.64 
5.64 
5.64 
5.64 


Sandstone 

<t 
(1 

M 
it 
U 
<t 
(( 
{( 
«t 
(( 
M 
U 
<( 
t( 
M 
M 
« 

« 

<« 
M 
It 


19 Months 

i( 

u 
it 
tt 

8 Months 
16 Months 

8 Months 

16 Months 

8 Months 
tt 

16 Months 
8 Months 
16 Months 
8 Months 
16 Months 
8 Months 
16 Months 


131 

146 

143 
138 

142 

144 

145 


285 
283 
288 
237 
363 
477 
313 
351 
206 
274 
187 
185 
68 
159 
202 
110 
245 
145 
142 
227 
131 
223 
242 
351 
203 
273 



Nos. 98-1 1 1 not plotted in Fig. 1. *Frost in stone. tWater 100 deg. Fahr. 
156 deg. Fahr. §Water contained 18.75% salt. tWater contained 12.5% salt. 



tWater 



sand and stone are increased, until they become zero for a mix- 
ture of 22.5 parts and 12.5 parts for the Portland and natural 
respectively. A straight-line formula of this kind furnishes a 
convenient analytical guide to show the variation in strength of 
different cement mixtures. 

Table II. is taken from tests reported by Mr. H. Von Schon, 
in the Transactions of the American Society of Civil Engineers 
for December, 1899, and shows results of Portland cement con- 
crete beams 6x6x18 inches span, tested to destruction by flexure. 
The average age of the specimens which set in air was about 60 
days. The sand was St. Mary's River; the broken sandstone was 
native Potsdam and the broken boulder stone was granitic. The 
broken stone all passed through a ij-inch ring and was retained 
on a i-inch ring. 

The table shows five different mixtures, varying in richness of 
cement from the *'D" mixture down to the "A" mixture. It 
will be seen that the richer mixtures always gave the highest 



Art. 26.] 



MODULUS OF RUPTURE IN BENDING. 



153 



results for ultimate fibre stress. The "E" mixtures, which were 
the leanest of the series, also contained a small percentage of 
lime. In no case did such a mix- 
ture attain the strength of any of 
the others. Figure 3 shows the re- 
sults of the table in graphic form. 
It is seen that no empiric equation 
can express these values. 

Table III. is compiled from Re- 
fKDrts of the Boston Transit Com- 
mission for the years 1901, 1902 
and 1903, and shows the ultimate 
fibre stress of Portland cement concrete beams when tested to 
destruction. The specimens represented in the first six lines 



£ 

O 

2 10 



^ 5 













V A 


nx 


X 
X 











100 200 300 400 

Modulus of Ruptuie in Lbs. per sq. in. 

FIG. 3. 



TABLE II.— PORTLAND CEMENT CONCRETE BEAMS, 
6x6xI8-INCH SPAN. 


Brand of 


Kind of 
Broken Stone 


Mixture 


No. of 
Tests 


Ultimate Fibre Stress— Lbs. per Sq. In. 


Cement 


Maximum 


Mean 


Minimum 


E 

E 

E 

E 

E 

E 

E 

E 

E 

E 

R 

R 

R 

R 

R 

R 

R 

R 

R 

R 


Sandstone 

ft 
Boulder Stone 

n n 

Sandstone 

44 

Boulder Stone 


A 
B 
C 
D 
E 
A 
B 
C 
D 
E 
A 
B 
C 
D 
E 
A 
B 
C 
D 
E 


2 
2 
2 
2 

2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 


178 
225 
288 
329 
108 
354 
358 
390 
420 
350 
181 
183 
266 
328 
195 
390 
423 
410 
411 
332 


176 

217 ■ 

280 

325 

102 

326 

328 

373 

410 

330 

169 

175 

262 

308 

182 

347 

406 

392 

393 

322 


174 
209 
272 
321 
97 
298 
299 
356 
400 
310 
158 
167 
258 
288 
169 
204 
390 
374 
375 
312 



Mixture A=l cement, 2.4 sand, 5.3 broken stone. 
Mixture B=l cement, 2.4 sand, 4.8 broken stone. 
Mixture C=l cement, 2.4 sand, 4.4 broken stone. 
Mixture D=l cement, 2.4 sand, 4.0 broken stone. 
Mixture E=l cement, 0.3 lime, 3.1 sand, 5.3 broken stone. 



were hand mixed; the next four were machine mixed; but the 
method of mixing the last two is not stated. The sand was 



154 



FLEXURAL PROPERTIES. 



[Ch. VII. 



clean and sharp; the crushed stone was trap rock, i to 2 J inches 
in size ; and the stone dust was finely crushed stone, varying from 

TABLE III.— PORTLAND CEMENT CONCRETE BEAMS, 
6x6x30-INCH SPAN. 





Composition 
by Volume 


Age 

in 

Days 


(0 

E 
08 

CQ 
o| 


Ultimate Fibre Stress 
in Lbs. per Sq. In. 


c 


C 
08 

L2 


C CO 

2 3 


4> 
> 

08 

k 




g 

2| 
oac/3 




Max. 


Mean 


Min. 




L8 


— 


30 


4 


640 


525 


442 




\.2 


— 


— 


1.8 


30 


7 


634 


571 


341 




L2 


— 


— 


1.8 


30 


5 


805 


651 


522 




1.2 


— 


— 


1.8 


136 


3 


1249 


993 


730 




L2 


— 


— 


1.8 


30 


14 


913 


689 


444 




— 


1.2 


— 


L8 


30 


33 


II2I 


783 


460 




— 


1.7 


— 


2.75 


30 


12 


999 


851 


677 




— 


1.9 


— 


2.6 


30 


50 


924 


850 


590 




— 


2. 


— 


2.4 


30 


30 


904 


731 


622 




— 


2. 


— 


2.4 


30 


100 


900 


728 


523 




2.5 


— 


— 


4. 


3Yrs. 


2 


972 


849 


726 




2.5 


— 


— 


4. 


" 


I 




809 









Remarks 



Kept in ground. 
Kept in ground; 26 in. span. 
Kept in ground; 30 in. span. 
Kept in ground all winter. 



(24 hours in compressed air 
lat 7 — 12 lbs. per sq. in, 
(24 hours in compressed air 
\ at 1 2 — 1 8 lbs. per sq. in. 

{48 hours in compressed air 
at 18—25 lbs. per sq. in. 
( 28—30 days in compressed 
(air at 20—25 lbs. per sq. in. 
Buried in sand under sea water. 
Buried in fresh earth. 



an impalpable powder to ^ inch in diameter. It will be seen 
that the beams mixed with stone dust give higher results than 
those mixed with sand. 

Table IV. is an abstract from the Report of the Boston Transit 

TABLE IV. 



No. of 
Beams 


Dimension . 


Modulus of Rupture in Lbs. 
per Sq. In. 


Average 
Days in 
Ground 


Remarks 


Tested 


Max'm 


Mean 


Minimum 


Ingredients 


4.... 

7 

5.... 

3.... 

I4.-.. 

33.... 


6x6x30 In. 

6x6x26 In. 
6x6x30 In. 


640 

634 
805 

1249 

913 

II2I 


525 

571 
651 

993 

683 

777 


442 

341 
522 

730 

444 

460 


28 

28 
28 

135 

28 
28 


i Cement; 

] Coarse, clean and sharp sand; 

( Gravel. 

(Cement; 

\ Coarse, clean and sharp sand; 

(Trap rock, 1 in. to 2% in. 

f Cement; 

J Coarse, clean and sharp sand; 

(Trap rock, 1 in. to 2J4 in. 

(Cement; 

< Coarse, clean and sharp sand; 

(Trap rock, 1 in. to 2^ in. 

( Same as above, but stone dust 

( instead of sand. 



Commission for 1901, and records the results of tests made on 
concrete beams 6x6x about 30 inches in length. The propor- 



Art. 26.] 



MODULUS OF RUPTURE IN BENDING. 



155 



tions of the ingredients of the concrete were i Vulcanite cement, 
2 sand and 4 broken stone of the character as shown in the col- 
umn headed ''Remarks." 

Table V. is taken from results recorded by E. C. Clarke in 
Vol. XIV. of the Transactions of the American Society of Civil 
Engineers, and shows the modulus of rupture obtained for beams 
10 inches square and about 6 feet long, which were buried in a 

TABLE V. 



Materials 



I Natural Cement 

1:3:7 

1:4:9 

1:6:11 



2 Sand : 5 Stone 



Modulus of Rupture in Lbs. per Sq. In. 



67 
176 
146 
112 



pit and tested when six months old. The stone used was screened 
pebbles, an inch or less in diameter. The modulus of rupture 
as calculated includes the weight of the beams. 

Table VI. is taken from the Report of the Boston Transit 
Commission for the year ending June 30, 1902, and gives values 
of the ultimate fibre stress of concrete beams in flexure. The 
cement was Vulcanite Portland. The mixing was done by hand 
and the beams were kept the first twenty-four hours in air and 

TABLE VI.— CONCRETE BEAMS 6x6x30 IN., 30 DAYS OLD. 



Composition by Volume 
(Approx.) 


No. of 
Tests 


Size of Stone Dust 


Ultimate Fibre Stress in Lbs. 
per Sq. In. 


Cement 


Sand 


Stone 
Dust 


Broken 
Stone 


Max. 


Mean 


Min. 


I 
I 
I 
I 


.9 

L6 

.9 


2 
.9 

.9 


2.4 
2.7 
3 
2.7 


4 
4 


Medium 
Coarse 


947 
846 
773 
862 


848 
784 
711 
806 


760 
704 
656 
739 



then twenty-nine days in damp earth. The results are of interest 
as showing the comparative strength of mixtures with stone dust 
and with sand. It will be seen that those beams in which the 
stone dust replaced the sand were the stronger and that in no 
case did the use of stone dust weaken the mixture. 

Table VII. is taken from some tests reported by T. S. Clark, 
in Engineering News of July 24, 1902, and shows the relation 



156 



FLEXURAL PROPERTIES, 



[Ch. VII. 



between the tensile strength of ordinary tensile briquettes and 
the extreme fibre stress of small concrete beams ixix8 inches. 
The same cement and aggregate were used for both kinds of 
tests and subjected to exactly the same treatment at the time of 
mixing. Each result shown is an average of from two to twelve 
specimens. All the mixtures were kept twenty-four hours in 
air, and the rest of the time presumably in water, although it is 
not so specifically stated. It will be seen that the ratio between 
the ultimate fibre stress in flexure as compared to the tensile 
strength varies from 1.32 to 1.66. 



TABLE VII. 



Composition of Specimen in 


Parts of 


Age 
in 










Cement 


Sand 


Stone 


Cinder 


Days 


Neat 


— 


— 


— 


30 


" 


— 


— 


— 


112 




lyi 


— 


— 


30 




2>^ 


— 


— 


60 




lYz 


— 


— 


112 




3 


— 


— 


28 




3 


— 


— 


56 




2 


3* 


— 


28 


1 


2 


— 


5 


30 



Ult. Tensile 

Strength in 

Lbs. per Sq. In. 



809 
932 
376 
482 
493 
282 
328 
187 

no 



Extreme Fibre 

Stress in 
Lbs. per Sq. In. 



1242 
1 406 
540 
634 
679 
417 
512 
304 
183 



Ratio of 

Tension to 

Bending 



1.53 
1.50 
1.43 
1.32 
1.37 
1.47 
1.56 
1.63 
1.66 



*Beams 3x3x30 inches. 

E. S. Wheeler records in the Report of the Chief of Engineers, 
U. S. Army, for 1896, p. 2870, an interesting series of tests, show- 
ing the relation between ultimate resistances of cement mixtures 
in tension, in bending and in compression ; the compression tests 
will not be considered, however, since crude apparatus was em- 
ployed. 

The results from the tension and bending experiments are per- 
haps comparable, although the actual tension values obtained 
may be erroneous, on account of the use of the ordinary tensile 
briquette. This statement applies similarly to the preceding 
table. The transverse specimens were 2x2x8 inches, broken on 
a 5 1-3-inch span. The specimens for the two kinds of tests 
were always prepared from the same batch of mortar ; each result 
in Table VIII. is an average of 4 to 10 breakings. It will be 
seen that the ratio of the extreme fibre resistance to the tensile 



Art. 27.] 



SHEARING RESISTANCE AND CONCLUSION 



157 



resistance averages about i^, having extreme values of i 1-4 to 
I 9-10. Experiments made with natural cements furnished sim- 
ilar results. 

Experiments by Durand-Claye (page 149) and by Bauschinger 
(page 2y) have already been noted, and their results check the 

TABLE VIII. 



Mixture 


Tensile Strength in Lbs. per Sq. In. 


Transverse Strength in Lbs. per Sq. In. 


Sand 


At Age of 


At Age of 


to 
Cement 


1 Day 


7 Days j 28 Ds. 


3 Mos. 


1 Year 


1 Day 


7 Days 


28 Ds. 


3 Mos. 1 Year 


Neat 
1:1 
1:2 
1:3 
1:5 


268 


588 1 698 
484 1 630 


733 
705 
491 
338 
187 




458 


III5 
607 
407 
247 


TO'^7 TO/<n 




721 


915 


II2I 
764 
541 
286 


1 185 








182 1 277 

1 


379 
252 




397 


582 
369 








1 









ratios obtained in Tables VII. and VIII.; in conclusion it may 
therefore be said that the value of the modulus is about ij times 
the ultimate tensile resistance of the same material when tested 
in the standard briquette form. It seems doubtful if anything 
more exact can at the present time be determined. 



Art. 27. — Transverse Shearing Resistance and Conclusion. 

The resistance of cement mixtures to shearing stresses has 
not been treated separately on account of the lack of experi- 
mental data. On page 2y are given the results of some tests by 
Bauschinger, and on page 95 some results obtained at Columbia 
University. It is only possible to state that the value of the ulti- 
mate shearing resistance varies between the extreme limits of 125 
to 375 pounds per square inch. The question of shear is of the 
greatest importance, and accurate and detailed experiments of 
the trasverse shearing resistance of concrete would be of great 
value. 

The elastic properties of reinforced concrete beams have not 
been discussed in this work, except in connection with results 
having direct bearing on ordinary cement mixtures; principally 
because, in the opinion of the author, the elastic behavior of the 
combination may be deduced by analysis, with the aid of the 



158 FLEXURAL PROPERTIES, [Ch. VII. 

experimental values found separately for the two elements. It 
is his opinion that the combination of the two materials acts in 
practice as rational theory might require, although some pub- 
lished experiments ascribe to concrete, when reinforced, dif¥erent 
elastic properties than when not reinforced. 



APPENDIX L 



REPORT ON UNIFORM TESTS OF CEMENT BY THE SPECIAL 

COMMITTEE OF THE AMERICAN SOCIETY 

OF CIVIL ENGINEERS 



'Presented at the Annual Meeting, January 21 , 190^, and Amended at the Annual 

Meeting, January 20, 1904. 



SAMPLING. 

I. — Selection of Sample. — The selection of the sample for testing is a detail 
that must be left to the discretion of the engineer ; the number and the quan- 
tity to be taken from each package will depend largely on the importance of 
the work, the number of tests to be made and the facilities for making them. 

2. — The sample shall be a fair average of the contents of the package; it is 
recommended that, where conditions permit, one barrel in every ten be 
sampled. 

3. — All samples should be passed through a sieve having twenty meshes 
per linear inch, in order to break up lumps and remove foreign material; this 
is also a very effective method for mixing them together in order to obtain an 
average. For determining the characteristics of a shipment of cement, the 
individual samples, may be mixed and the average tested; where time will 
permit, however, it is recommended that they be tested separately. 

4. — Method of Sampling. — Cement in barrels should be sampled through a 
hole made in the centre of one of the staves, midway between the heads, or in 
the head, by means of an auger or a sampling iron similar to that used by 
sugar inspectors. If in bags, it should be taken from surface to centre. 

CHEMICAL ANALYSIS. 
5. — Significance. — Chemical analysis may render valuable service in the 
detection of adulteration of cement with considerable amounts of inert mate- 
rial, such as slag or ground limestone. It is of use, also, in determining 
whether certain constituents, believed to be harmful when in excess of a cer- 
tain percentage, as magnesia and sulphuric anhydride, are present in inadmissi- 
ble proportions. While not recommending a definite limit for these impurities. 



160 



METHODS OF TESTING CEMENT BY 



the Committee would suggest that the most recent and reliable evidence ap- 
pears to indicate that magnesia to the amount of ^%, and sulphuric anhydride 
to the amount of 1.75%, may safely be considered harmless. 

6. — The determination of the principal constituents of cement — silica, 
alumina, iron oxide and lime — is not conclusive as an indication of quality. 
Faulty character of cement results more frequently from imperfect preparation 
of the raw material or defective burning than from incorrect proportions of the 
constituents. Cement made from very finely ground material, and thoroughly 
burned, may contain much more lime than the amount usually present and still 
be perfectly sound. On the other hand, cements low in lime may, on account 
of careless preparation of the raw material, be of dangerous character. 
Further, the ash of the fuel used in burning may so greatly modify the com- 
position of the product as largely to destroy the significance of the results of 
analysis. 

7. — Method. — As a method to be followed for the analysis of cement, that 
proposed by the Committee on Uniformity in the Analysis of Materials for the 
Portland Cement Industry, of the New York Section of the Society for Chem- 
ical Industry, and published in the Journal of the Society for January I3th, 
1902, is recommended. 

SPECIFIC GRAVITY. 

8. — Significance. — The specific gravity of cement is lowered by underburn- 
ing, adulteration and hydration, but the adulteration must be in considerable 

quantity to affect the results appreci- 
ably. 

9. — Inasmuch as the differences in 
specific gravity are usually very 
small, great care must be exercised 
in making the determination. 

10. — When properly made, this test 
affords a quick check for under- 
burning or adulteration. 

II. — Apparatus and Method. — The 
determination of specific gravity is 
most conveniently made with Lc 
Chatelicr's apparatus. This consists 
of a flask (D), Fig. I, of 120 cu. cm. 
(7.32 cu. ins.) capacity, the neck of 
which is about 20 cm. (7.87 ins.) long; 
in the middle of this neck is a bulb 




Le Chatelier's Specific Gravity Apparatus. 
FIG. 1. 



(C), above and below which are two marks (F) and (£"); the volume between 
these marks is 20 ou. cm. (1.22 cu. ins.). The neck has a diameter of about 9 
mm. (0.35 in.), and is graduated into tenths of cubic centimeters above the bulb. 

12.— Benzine (62° Baume naphtha), or kerosene free from water, should 
be used in making the determination. 

13. — The specific gravity can be determined in two ways^ 



THE AMERICAN SOCIETY OF CIVIL ENGINEERS. 1 6 1 

(l) The flask is filled with cither of these liquids to the lower mark {E , 
and 64 gr. (2.25 oz.) of powder, previously dried at 100° Cent. (212° Fahr. ) 
and cooled to the temperature of this liquid, is gradually introduced through 
the funnel (B) [the stem of which extends into the flask to the top of the 
bulb (C)], until the upper mark {F) is reached. The difference in weight 
between the cement remaining and the original quantity (64 gr. j is the weight 
which has displaced 20 cu. cm. 

14. — (2) The whole quantity of the powder is introduced and the level of 
the liquid rises to some division of the graduated neck. This reading plus 
20 cu. cm. is the volume displaced by 64 gr. of the powder. 

13. — The specific gravity is then obtained from the formula: 

_ . ^ Weight of Cement 

Specific Gravity=— — -— — 

Displaced Volume. 

16. — The flask, during the operation, is kept immersed in water in a jar 
(y^), in order to avoid variations in the temperature of the liquid. The 
results should agree within O.OI. 

17. — A convenient method for cleaning the apparatus is as follows: The 
flask is inverted over a large vessel, preferably a glass jar, and shaken ver- 
tically until the liquid starts to flow freely ; it is then held still in a vertical 
position until empty ; the remaining traces of cement can be removed in a 
similar manner by pouring into the flask a small quantity of clean liquid and 
repeating the operation. 

18. — More accurate determinations may be made with the picnometer. 

FINENESS. 

19. — Significance. — It is generally accepted that the coarser particles in 
cement are practically inert, and it is only the extremely fine powder that 
possesses adhesive or cementing qualities. The more finely, cement is pul- 
verized, all other conditions being the same, the more sand it will carry and 
produce a mortar of a given strength. 

20. — The degree of final pulverization which the cement receives at the 
place of manufacture is ascertained by measuring the residue retained on 
certain sieves. Those known as the No. 100 and No. 200 sieves are recom- 
mended for this purpose. 

21.— Apparatus. — The sieves should be circular, about 20 cm. (7.87 ins.) 
in diameter, 6 cm. (2.36 ins.) high, and provided with a pan, 5 cm. (1.97 ins.) 
deep, and a cover. 

22. — The wire cloth should be woven (not twilled) from brass wire having 
the following diameters ; 

No. 100, 0.0045 in.; No. 200, 0.0024 in. 
23. — This cloth should be mounted on the frames without distortion ; the 
mesh should be regular in spacing and be within the following limits: 
No. 100, 96 to 100 meshes to the linear inch. 
No. 200, 188 to 200 " '* " ** 



162 



METHODS OF TESTING CEMENT BY 



24. — Fifty grams (l.76oz.) or 100 gr. (3.52 oz.) should be used for the 
test, and dried at a temperature of 100° Cent. (212° Fahr. ) prior to sieving. 

25. — Method. — The Committee, after careful investigation, has reached the 
conclusion that mechanical sieving is not as practicable or efficient as hand 
work, and, therefore, recommends the following method : 

26. — The thoroughly dried and coarsely screened sample is weighed and 
placed on the No. 200 sieve, which, with pan and cover attached, is held in 
one hand in a slightly inclined position, and moved forward and backward, at 
the same time striking the side gently with the palm of the other hand, at the 
rats of about 200 strokes per minute. The operation is continued until not 
more than one-tenth of I % passes through after one minute of continuous 
sieving. The residue is weighed, then placed on the No. 100 sieve and the 
operation repeated. The work may be expedited by placing in the sieve a 
small quantity of large shot. The results should be reported to the nearest 
tenth of I per cent 

NORMAL CONSISTENCY. 

27. — Significance. — The use of a proper percentage of water in making the 
pastes* from which pats, tests of setting and briquettes are made, is exceed- 
ingly important, and affects vitally the results obtained. 

28. — The determination consists in measuring the amount of water required 
to reduce the cement to a given state of plasticity, or to what is usually desig- 
nated the normal consistency. 

29. — Various methods have been proposed for making this determination, 
none of which has been found entirely satisfactory. The Committee recom- 
mends the following : 

30. — Method, yicat Needle Apparatus. — This consists of a frame (A'), Fig. 

2, bearing a movable rod (L), with the 
cap {A) at one end, and at the other 
end the cylinder (5), I cm. (0.39 in.) in 
diameter, the cap, rod and cylinder weigh- 
ing 300 gr. ( 10.58 oz.). The rod, which 
can be held in any desired position by a 
screw {F)r carries an indicator, which 
moves over a scale (graduated to centi- 
meters) attached to the frame (A'). The 
paste is held by a conical, hard-rubber 
ring (/), 7 cm. (2.76 ins.) in diameter at 
the base, 4 cm. (1.57 ins. ) high, resting on 
a glass plate (/), about 10 cm. (3.94 ins.) 
square. 

31. — In makingthe determination, the same quantity of cement as will be 
subsequently used for each batch in making the briquettes (but not less than 




Vicat Needle. 
FIG. 2. 



*The term "paste" is used in this report to designate a mixture of cement and water, 
and the word "mortar" a mixture of cement, sand and water. 



THE AMERICAN SOCIETY OF CIVIL ENGINEERS. 1 63 

500 grammes) is kneaded into a paste, as described in Paragraph 58/ and 
quickly formed into a ball with the hands, completing the operation by tossing 
it six times from one hand to the other, maintained 6 ins. apart; the ball is 
then pressed into the rubber ring, through the larger opening, smoothed off 
and placed on a glass plate (on its large end) and the smaller end smoothed 
off with a trowel; the paste, confined in the ring, resting on the plate, is 
placed under the rod bearing the cylinder, which is brought in contact with 
the surface and quickly released. 

32. — The paste is of normal consistency when the cylinder penetrates to 
a point in the mass 10 mm. (0.39 in.) below the top of the ring. Great care 
must be taken to fill the ring exactly to the top. 

33-— The trial plates are made with varying percentages of water until 
the correct consistency is obtained. 

34. — The Committee has recommended, as normal, a paste the consistency 
of which is rather wet, because it believes that variations in the amount of 
compression to which the briquette is subjected in moulding are likely to be 
less with such a paste. 

35- — Having determined in this manner the proper percentage of water re- 
quired to produce a neat paste of normal consistency, the proper percentage 
required for the sand mortars is obtained from an empirical formula. 

36. — The Committee hopes to devise such a formula. The subject proves 
to be a very difficult one, and, although the Committee has given it much study, 
it is not yet prepared to make a definite recommendation. 

TIME OF SETTING. 

37. — Significance. — The object of this test is to determine the time which 
elapses from the moment water is added until the paste ceases to be fluid and 
plastic (called the "initial set"), and also the time required for it to acquire a 
certain degree of hardness (called the "final" or "hard set"). The former 
of these is the more important, since, with the commencement of setting, the 
process of crystallization or hardening is said to begin. As a disturbance of 
this process may produce a loss of strength, it is desirable to complete the 
operation of mixing and moulding or incorporating the mortar into the work 
before the cement begins to set. 

38. — It is usual to measure arbitrarily the beginning and end of the setting 
by the penetration of weighted wires of given diameters. 

39. — Method. — For this purpose the Vicat Needle, which has already been 
described in Paragraph 30, should be used. 

40. — In making the test, a paste of normal consistency is moulded and 
placed under the rod (Z.), Fig, 2, as described in Paragraph 31; this rod. Bear- 
ing the cap (D) at one end and the needle (//), I mm. (0.039 in.) in diameter, 
at the other, weighing 300 gr. (10.38 oz.). The needle is then carefully brought 
in contact with the surface of the paste and quickly released. 

41. — The setting is said to have commenced when the needle ceases to pass 
a point 5 mm. (0.20 in.) above the upper surface of the glass plate, and is 



164 



METHODS OF TESTING CEMENT BY 



said to have terminated the moment the needle does not sink visibly into the 
mass. 

42. — The test* pieces should be stored in moist air during the test; this is 

accomplished by placing them on a rack over 

j water contained in a pan and covered with 

I a damp cloth, the cloth to be kept away from 

them by means of a wire screen; or they may 

be stored in a moist box or closet. 

43. — Care should be taken to keep the 
needle clean, as the collection of cement on 
the sides of the needle retards the penetra- 
tion, while cement on the point reduces the 
area and tends to increase the penetration. 

44. — The determination of the time of set- 
ting is only approximate, being materially 
affected by the temperature of the mixing 
water, the temperature and humidity of the air 
during the test, the percentage of water used, 
and the amount of moulding the paste re- 
ceives. 




Details for BriqueUe. 
FIG. 3. 



STANDARD SAND. 



45. — The Committee recognizes the grave objections to the standard quartz 
now generally used, especially on account of its high percentage of voids, the 
difficulty of compacting in the moulds, and its lack of uniformity; it has 
spent much time in investigating the various natural sands which appeared to 
be available and suitable for use. 

46. — For the present, the Committee recommends the natural sand from 
Ottawa, 111., screened to pass a sieve having 20 meshes per linear inch and 
retained on a sieve having 30 msshes per linear inch ; the wires to have diam- 
eters of 0.0165 and 0.0II2 in., respectively, /'. e., half the width of the opening 
in each case. Sand having passed the No. 20 sieve shall be considered stand- 
ard when not more than one per cent, passes a No. 30 sieve, after one minute 
continuous sifting of a 500-gram sample. 

47. — The Sandusky Portland Cement Company, of Sandusky, Ohio, has 
agreed to undertake the preparation of this sand, and to furnish it at a price 
only sufficient to cover the actual cost of preparation. 



FORM OF BRIQUETTE. 

48. — While the form of the briquette recommended by a former Com- 
mittee of the Society is not wholly satisfactory, this Committee is not pre- 
pared to suggest any change, other than rounding off the corners by curves of 

^-in. radius. Fig. 3. 

MOULDS. 

49- — The moulds should be made of brass, bronze or some equally non- 




THE AMERICAN SOCIETY OF CIVIL ENGINEERS. 1 65 

corrodible material having sufficient metal in the sides to prevent spreading 
during moulding. 

30. — Gang moulds, which permit 
moulding a number of briquettes at 

one time, are preferred by many to 

<^;«wi^ .,,-^..1^^. c-.^^^ tU^ rt^^^t^- Details for Gang Mould, 

single moulds; since the greater ^ 

quantity of mortar that can be mixed 

tends to produce greater uniformity in the results. The type shown in Fig. 4 

is recommended. 

51. — The moulds should be wiped with an oily cloth beiorc using. 

MIXING. 

52. — All proportions should be stated by weight; the quantity of water to 
be used should be stated as a percentage of the dry material. 

53. — The metric system is recommended because of the convenient relation 
of the gram and the cubic centimeter. 

54. — The temperature of the room and the mixing water should be as near 
21° Cent. (70° Fahr.) as it is practicable to maintain it. 

55- — The sand and cement should be thoroughly mixed dry. The mixing 
should be done on some non-absorbing surface, preferably plate glass. If the 
mixing must be done on an absorbing surface it should be thoroughly dampened 
prior to use. 

56. — The quantity of material to be mixed at one time depends on the 
number of test pieces to be made; about 1,000 gr. (35>28 oz.) makes a conven- 
ient quantity to mix, especially by hand methods. 

57. — The Committee, after investigation of the various mechanical mixing 
machines, has decided not to recommend any machine that has thus far been 
devised, for the following reasons: 

(I) The tendency of most cement is to "ball up" in the machine, thereby 
preventing the working of it into a homogeneous paste; (2) there are no means 
of ascertaining when the mixing is complete without stopping the machine, and 
(3) the difficulty of keeping the machine clean. 

33. — Method. — The material is weighed and placed on the mixing table, 
and a crater formed in the centre, into which the proper percentage of clean 
water is poured; the material on the outer edge is turned into the crater by the 
aid of a trowel. As soon as the water has been absorbed, which should not 
require more than one minute, the operation is completed by vigorously 
kneading with the hands for an additional 1)4 minutes, the process being 
similar to that used in kneading dough. A sand-glass affords a convenient 
guide for the time of kneading. During the operation of mixing the hands 
should be protected by gloves, preferably of rubber. 

MOULDING. 
59. — Having worked the paste or mortar to the proper consistency, it is at 
once placed in the moulds by hand. 

60. — The Committee has been unable to secure satisfactory results with the 



166 



METHODS OF TESTING CEMENT BY 



present moulding machines; the operation of machine moulding is very slow, 
and the present types permit of moulding but one briquette at a time, and are 
not practicable with the pastes or mortars herein recommended. 

61. — Method. — The moulds should be filled at once, the material pressed in 
firmly with the fingers and smoothed off with a trowel without ramming; the 
material should be heaped up on the upper surface of the mould, and, in 
smoothing off, the trowel should be drawn over the mould in such a manner as 
to exert a moderate pressure on the excess material. The mould should be 
turned over and the operation repeated. 

62. — A check upon the uniformity of the mixing and moulding is afforded 
by weighing the briquettes just prior to immersion, or upon removal from the 
moist closet. Briquettes which vary in weight more than 3 per cent from the 
average should not be tested. 

STORAGE OF THE TEST PIECES. 

63. — During the first 24 hours after moulding the test pieces should be kept 
in moist air to prevent them from drying out. 

64. — A moist closet or chamber is so easily devised that the use of the damp 
cloth should be abandoned if possible. Covering the test 
pieces with a damp cloth is objectionable, as commonly 
used, because the cloth may dry out unequally, and, in 
consequence, all the test pieces arc not maintained under 
the same condition. Where a moist closet is not avail- 
able, a cloth may be used and kept uniformly wet by 
immersing the ends in water. It should be kept from 
direct contact with ths test pieces by means of a wire 
screen or some similar arrangement. 

63. — A moist closet consists of a soapstone or slate 
box, or a metal-lined wooden box — the metal lining being 
covered with felt and this felt kept wet. The bottom of 
the box is so constructed as to hold water, and the sides 
are provided with cleats for holding glass shelves on which 
to place the briquettes. Care should be taken to keep the 
air in the closet uniformly moist. 

66. — After 24 hours in moist air the test pieces for 
longer periods of time should be immersed in water main- 
tained as near 21° Cent. (70° Fahr. ) as practicable; they may be storied in 
tanks or pans, which should be of non-corrodible material. 




Form of Clip. 
FIG. 5. 



TENSILE STRENGTH. 

67. — The tests -may be made on any standard machine. A solid metal 
clip, as shown in Fig. 5/ is recommended. This clip is to be used without 
cushioning at the points of contact with the test specimen. The bearing at 
each point of contact should be X i^- wide, and the distance between the cen- 
tre of contact on the same clip should be \% ins. 



THE AMERICAN SOCIETY OF CIVIL ENGINEERS. 167 

68. — Test pieces should be broken as soon as they are removed from the 
water. Care should be observed in centring the briquettes in the testing ma- 
chine, as cross-strains, produced by improper centring, tend to lower the break- 
ing strength. The load should not be applied too suddenly, as it may produce 
vibration, the shock from which often breaks the briquette before the ultimate 
strength is reached. Care must be taken that the clips and the sides of the 
briquette be clean and free from grains of sand or dirt, which would prevent a 
good bearing. The load should be applied at the rate of 600 lbs. per minute. 
The average of the briquettes of each sample tested should be taken as the 
test, excluding any results which are manifestly faulty. 

CONSTANCY OF VOLUME. 

69- — Significance. — The object is to develop those qualities which tend to 
destroy the strength and durability of a cement. As it is highly essential to de- 
termine such qualities at once, tests of this character are for the most part 
made in a very short time, and are known, therefore, as accelerated tests. 
Failure is revealed by cracking, checking, swelling or disintegration, or all of 
these phenomena. A cement which remains perfectly sound is said to be of 
constant volume. 

70. — Methods. — Tests for constancy of volume are divided into two classes: 
(I) normal tests, or those made in either air or water maintained at about 21° 
Cent. (70° Fahr. ), and (2) accelerated tests, or those made in air, steam or 
water at a temperature of 45° Cent. (115° Fahr.) and upward. The test pieces 
should be allowed to remain 24 hours in moist air before immersion in water 
or steam or preservation in air. 

71. — For these tests, pats, about 7^ cm. (2.95 ins.) in diameter, \% cm. 
(0.49 in.) thick at the centre, and tapering to a thin edge, should be made, upon 
a clean glass plate [about 10 cm. (3.94 ins.) square], from cement paste of 
normal consistency. 

72. — Normal Test. — A pat is immersed in water maintained as near 21° 
Cent. (70° Fahr.) as possible for 28 days, and observed at intervals; the pat 
should remain firm and hard and show no signs of cracking, distortion or 
disintegration. A similar pat is maintained in air at ordinary temperature, and 
observed at intervals. 

73. — Accelerated Test. — A pat is exposed in any convenient way in an 
atmosphere of steam, above boiling water, in a loosely closed vessel, for three 
hours. 

74. — To pass these tests satisfactorily the pats should remain firm and 
hard, and show no signs of cracking, distortion or disintegration. 

75. — Should the pat leave the plate, distortion may be detected best with a 
straight-edge applied to the surface which was in contact with the plate. 

76. — In the present state of our knowledge it cannot be said that cement 
should necessarily be condemned simply for failure to pass the accelerated 



168 METHODS OF TESTING CEMENT, 

tcstsj nor can a cement be considered entirely satisfactory simply because it 
has passed these tests. 

Submitted on behalf of the Committee. 

GEORGE S. WEBSTER, 

Chairman. 
RICHARD L. HUMPHREY, 

Secretary. 
Committee. 
GEORGE S. WEBSTER, 
RICHARD L. HUMPHREY, 
GEORGE F. SWAIN, 
ALFRED NOBLE, 
LOUIS C. SABIN, 
S. B. NEWBERRY, 
CLIFFORD RICHARDSON, 
W. B. W. HOWE, 
F. H. LEWIS. 



APPENDIX IL 



CONSTITUTION OF PORTLAND CEMENT. 

Clifford Richardson, in a paper read before the Association of Portland 
Cement Manufacturers, at Atlantic City, June 15. 1904, has advanced consid- 
erably the knowledge concerning the constitution of Portland cements. 

Le Chatelier and, independently of him, Tdrncbohm have found, as a result 
of studies by microscopic methods, that clinker consists of four constituents — 
alit, belit, celit and felit, whose sections have distinct optical properties, and 
of a fifth amorphous isotropic mass which has no action upon polarized light 
Alit and celit are the principal constituents of clinker. 

Richardson, from his own work, concludes that clinker is a solid solu- 
tion of silicates and aluminates; alit being a solution of tricalcic aluminate 
(Al2033.CaO), in tricalcic silicate (SiOa 3CaO), and celit a solution of dicalcic 
aluminate (Al203.2CaO) in dicalcic silicate (Si02.2CaO). The presence of 
iron, magnesia, etc., exerts no essential influence, although probably adding to 
the complexity of the solid solutions present. 

The formation of clinker from pure chemicals at a temperature below fusion 
is probably due to diffusion and subsequent interaction; this has been shown 
for other solid substances, as, for example, in the production of barium sulphate 
and sodium carbonate from a finely pulverized mixture of sodium sulphate and 
barium. carbonate maintained in continued close contact. 

Concerning, therefore, the manufacture of cements Richardson states, from 
the viewpoint of the diffusion of solid substances, as shown by the above 
example, that finer grinding of the raw mixture would make possible the use 
of lower temperatures in burning, and that therefore the relative costs of fuel 
and fineness of grinding at any given locality will determine, from an econ- 
omic standpoint, the fineness to which the raw materials should be ground. 

Richardson's work, while not settling the constitution of cement mixtures, 
is of the greatest importance, not only for what it has already accomplished, 
but also for the possibilities and methods of investigation it suggests; and it 
may reasonably be expected that in a relatively short time the question of the 
constitution of cements will be made as clear as is that of the different forms 
of iron. His work corroborates the conclusion, previously stated in Chapter I., 
that a simple chemical analysis of the constituents present in a cement can, as 
yet, furnish little evidence of its quality or as to its fitness for use. 



INDEX. 

PAGE 

Accelerated tests 39, 167 

Adhesion of iron in concrete 61-66 

Aggregate ; character of, effect on strength 30-39 

Analyses of natural cement 6-8 

Analyses of Portland cement 3-6 

Beams, concrete 142-158 

Bending (see flexure). 

Blowing of cements 3, 39 

Briquette, form of, for tensile testing I64 

Chemical analyses 3-8, 159 

Cinder concretes in compression 83, III, 1 13 

Cinder concretes in tension 78 

Clay, effect of, on strength 34-39 

Coefficient of elasticity, explained 70-75 

Coefficient of elasticity, in compression 99-121 

Coefficient of elasticity, in flexure I44-I49 

Coefficient of elasticity, in tension 75-98 

Coefficient of linear thermal expansion 43-45 

Cold, effect of, on cement mixtures 55-61 

Commercial physical tests, discussed 9-39 

Commercial physical tests, of American Soc. of Civ. Eng 159-168 

Compression, author's conclusions on I32-I4I 

Compression, coefficient of elasticity 91, 95/ 96, 99-121 

Compression, coefficient of elasticity compared to tensile coefficient, 

83, 88, 141 . 

Compression, ultimate resistance to 83, 99-141 

Compression, ultimate resistance to, hardening in sea water 47 

Compression, ultimate resistance to, effect of size of specimen 106 

Compression, ultimate resistance to, use of cushions 108 

Compression; ultimate resistance compared to tensile resistance 26-29 

Consistency, normal 162 

Constancy of volume, test of 39, 167 

Constitution of Portland cement 1-8, 169 

Contraction of cements on hardening 40-43 

Crushing (see compression). 



172 INDEX, 

PAGE 

Curves, stress-strain, explained 70-75 

Curves, stress-strain, for compression. . 88-95, 103, 107-109, 112, II6-II8, 120 
Curves, stress-strain, for tension 81, 88-95 

Definition of a cement I 

Disintegration of cement mixtures, in sea waters 45-47, 52 

Dry concrete against wet (see wet . 

Effect of freezing 55-61 

Elastic limit, explained 71 

Expansion, due to temperature changes 43-45 

Expansion of cements during setting 40-43 

Fatigue of cement mixtures 66-69 

Fibre stress, extreme, in concrete beams 146-158 

Final setting of cements 13, I63 

Fineness test I I-I3, I6I 

Fineness of sands, effect of, in tensile strength 30-39 

Flexural coefficient of elasticity I44 

Flexural properties of cement mixtures 142-158 

Freezing, effect of 55-61 

High temperatures 1 32 

Hot water test 39 

Impervious concrete 51-55 

Initial setting 13, 163 

Loam in sands .• 34-39 

Magnesia, limit of, in cement 3 

Manufacture of cement 9 

Mica, effect of 129 

Mixing cement for testing 165 

Modulus of elasticity (see coefficient of elasticity). 

Modulus of rupture in flexure I46-I58 

Modulus of rupture, ratio to tensile stress 157 

Moulds, for tensile tests 164 

Natural cement, definition I 

Permeability of cement mixtures 51 -55 

Plaster of paris, action in delaying set I4 

Plaster of paris, effect on strength when setting is retarded 18 

Plaster of paris, effect on variation of volume during setting 4I 

Plaster of paris, limit of, in cements 3 

Plasticity of concretes (see wet). 

Porosity 51-55, 140 

Portland cement, definition I 

Pozzalana, addition of, to cements 45-51 



INDEX. 173 

PAGE 

Rate of application of stress to concrete 67 

Ratio of modulus of rupture to tensile resistance 157 

Reinforced concrete, tests in tension 76 

Reinforced concrete, author's opinion on 157 

Repeated applications of stress 66, 100 

Repeated applications of stress, effect on coefficient of elasticity 73 

Resistance to stress (sec tension, compression, flexure, shear). 

Retarding setting of cements 57 

Rods, adhesion of iron, in concrete 61-66 

Salt, effect of, in gauging 50, 56 

Sampling cement for purposes of test 159 

Sands, variation of, in tensile tests 30-39 

Sands, washed vs. unwashed 35-39 

Screenings (rock) in place of sand 30-39, 155 

Sea water, action of 45-5 1 

Sea water, strength in 47-5 1 

Setting, effect of plaster of paris on I4 

Setting, tests for time of 13-19, 163 

Setting, theories of 1 , 1 69 

Setting under water I30 

Shear, adhesive (see adhesion). 

Shear, transverse, ultimate resistance to 27, 95, I48, 157 

Shrinkage during setting 40-43 

Sieves, size of 12, 161 

Solution, solid, cement as a 169 

Specific gravity tests 10, 160 

Standard sand for tensile tests I64 

Storage of test pieces 166 

Straight line formula for coefficient of elasticity 132-138 

Straight line formula for ultimate resistance 1 38-141 

Strength, gauged with salt water , 50 

Strength in sea water 47 

Strength (see tension), compression, flexure, shear. 
Stress-strain curves (sec curves). 

Temperature changes during setting 18 

Temperature, effect of, on setting 16 

Temperature, effect of high, on ultimate resistance 132 

Tensile properties, coefficient of elasticity and ultimate resistance 75-98 

Tensile properties, conclusions as to 97 

Tensile strength, effect on of variations of sands 30-39 

Tensile strength, tests of, on standard briquettes 19-26, 166 

Tensile strength, tests of, hardening in sea water 47 

Tensile strength, ratio of, to compressive strength 26-29 

Tensile strength, variations in methods of determining 29 



174 INDEX. 

PAGE 

Tests, commercial 9 

Theory of flexure, applied to concrete I42 

Thermal expansion, coefficient of 43-45 

Time of setting (sec setting). 

Twisted rods vs. plain rods, adhesion 61 

Ultimate resistance in compression 99-141 

Ultimate resistance in tension 75-98 

Ultimate resistance in flexure I46-I38 

Ultimate resistance in transverse shear 27, 157 

Variation in volume, during setting 40-43 

Variation in volume, due to temperature 43-45 

Variation of stone in concrete, effect on ultimate resistance 129 

Vicat needle 162 

Water, hardening under I30 

Wet vs. dry concretes 82, 121, I30 



AUTHORS' INDEX. 



{Italics Indicate Journals. ) 



PAGE 

Adie 44 

American Society of Civil Engineers, 
Transactions of.... 6, 9, 12, 13, 21, 23, 35, 
40, 42, 50, 53, 66, 118, 123, 144, 152, 155, 159 
American Society for Testing Materi- 
als, Proceedings of. . 32, 51, 59, 63, 83, 119 
Annates des Fonts et Chausees — 20, 31, 33, 
43, 45, 52, 65, 66, 75, 148 
Arsenal Reports; see Watertown. 

Assoc. Eng. Societies, Journ. of. 24 78 

Austrian Society of Civil Engineers. . . 

92, 96, 136 

Bach,C 71, 99-105, 133, 138 

Baker, B 103 

Baker, I. 123 

Bauschinger, J 26, 27, 41, 44, 157 

Berger and Guillerme 20, 44 

Beton u. Eisen 61 

Black, A 33 

Boston Transit Commission. . . 5, 43, 48, 153 

Bouniceau 43 

Brown, W. L 147 

Busing and Schumann 27, 44, 48 

Canadian Society Civil Engrs. , Tra ns. of 60 

Candlot 45 

Carleton, R. A. W 147 

cnief Engr. U. S. Army; see United 
States Army. 

Christophe 44 

Civil Ingejdeur, Der 103 

Clark, T. F 34, 129, 155 

Clarke, E. C. 13, 21, 23, 26, 35, 50, 155 

Coelos, J. A 147 

Considere 42, 65 

Costigan, J. S 60 

Cummings, U 6 

De Joly 65, 66, 75 

Derleth.W.T 84, 134 

Deutscher Ingenieure; see Zeitsch. des 

Ver. 
Dougherty, R. E 44 



PAGE 

Doyle, T. L 131 

Durand-Claye 44, 148, 157 

Dyckerhoff 47 



Engineering News.. 33, 34, 35, 36, 129, 131, 155 
Engineering Record 37 



Falk, M. S 84, 144 

Feret, R 31, 33, 46, 49, 52, 54, 138 

Fuller, W. 8 138 

Gary, M 42 

German Portland Cement Manufac- 
turers' Society 47 

Gillmore, Q. A 16, 105 

Gowen, C. S 50, 59 

Grant, J 13, 25, 26, 41, 126 

Griesenauer, S. J 35 

Guillerme 20, 44 

Hallock, W 45 

Hartig 103 

Hatt, W. K 63, 83, 136 

Hawkesworth, J 84, 134 

Heath 50 

Henby,W. H 78, HI 

Holman, M. L 21 

Hunt, R. W.,&Co 24 

Institution of Civil Eng., Gt. Brit.. Pro- 
ceedings 13, 25, 26, 41, 49, 53, 126, 147 

Journal of Assoc. Eng. Societies ; see 
Assoc. 

Johnson, J. B 24, 26 

Justice, E. R : 131 

Lanza, G 147 

Lamed, E. S 32 

Lathbury & Spackman, Inc 5, 13, 25 

Le Chatelier 1, 8, 45 

Lesley, R. W. 24, 53 



176 



AUTHORS' INDEX. 



PAGE 

Marburg, E 119 

McCaustland, E J 118, 138, 146 

McCurdy, H. S. R 43 

Meier 44 

Michaelis 45 

Mills, C M 37 

Mineral Industry 12 

Morsch , E 61 

Newberry, S. B. and W. B 1, 8 

New York, Report of State Engr. 24, 121, 124 
Noble, A. 50 

Pence, W. D 43 

Fonts et CJiaussees ; see Annates, 

Rae, J. G 44 

Rafter, Geo. W 24, 116, 121, 137, 138 

Ries & Eckels 5 

Sherman, C. E • 36 

Schumann, C 27, 42, 44, 48 

Spofford,C 61 

Sussex, J. W 130 

Swain, G.F 40 



PAGE 

Technograph, Univ. of Illinois 131 

Testing Materials; see American So- 
ciety for ; Proceedings. 

Tetmajer 26 

Tornei 42 

Transactions; see American Society of 
Civil Eng.; see Canadian Society of 
Civil Eng. 

United States Army; Report CJiief of 

Engrs 15, 17, 30, 56, 63, 149, 156 

Unwin, W. C 26 

Van Ornum, J. L 66 

Von Schon, H 152 



Watertown Arsenal Reports 3, 4, 10, 14, 

17, 18, 28, 56, 58, 64, 74, 105, 113, 

121, 125, 127, 130, 132, 135, 137, 139 

Western Society of Engrs., Proceed, of, 43, 84 

Wheeler, E. S 15, 17, 30, 56, 63, 149, 156 

Whittemore, D. T 6 

Zeitschrift des Ver. Deutscher Inge- 
nieure 71, 99 



W 73 




















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